The cab pulled up at the entrance to a residential square in Islington. It was typical of terraced housing in the area, with a small green commons surrounded by identical row houses in the Georgian style. It showed signs of the various ups and downs the area had suffered over the years, but in general it appeared to be on an upswing; the houses were in good shape and the commons done up as a pleasant little park.

Sherlock stepped out of the cab, stood just enough out of the way for everyone else to get out without bumping into him, and gave the street a critical once-over. “I’ve been here before.”

“Of course you have,” Hermione sighed.

“I don’t recognize it,” said John. “Was this when …?”

“No, it was before you and I met,” said Sherlock, pacing slowly down the pavement. “It was when I was just getting started with the Met. Cases were few and far between, and I needed to keep myself from getting seriously bored. So I basically memorized London. Started with the streets, of course – I could qualify to be a cabbie if I wanted.”

“Probably better than most of them. As long as you don’t branch out into serial killing,” said John, remembering their first case together.

“That’s been done. Anyway, once I’d got the streets down, I walked them all. Studied them all. Noticed the anomalies. Did you know, for example, that there are precisely thirty-seven missing houses in London?”

“Like Leinster Gardens?” asked Mary, shivering. She really didn’t like to think about what had happened and almost happened there, although things had worked out in the end.

“Well no, Leinster Gardens has house numbers and fake house fronts but there’s a physical gap where the houses themselves are missing. These missing houses are just … not there. Gaps in the sequence where there’s no reason for there to be a gap, but no actual gap between houses. A street with eight houses on one side and seven identical houses and a missing number on the other side. And nobody notices that it takes forty paces to walk from the north end of the street to the south, but forty-four from south to north, only on the side with the missing number.”

“Nobody?” asked John.

“Nobody except obsessive-compulsive consulting detectives. So much is written off as anomalies caused by houses destroyed in the war, burned and rebuilt, reconstruction and remodelling, and so forth … and of course there are some of those, I had to account for all of that, too. These thirty-seven are the ones that can’t be explained that way. I was planning to write a monograph on the subject. Then I got onto an intriguing case involving jewellery thefts committed by trained monkeys and somehow never got around to it.” He spun on his heel to face Hermione while still walking in the same direction, only now backwards. “Do I have your people to thank for that, Miss Granger?”

“Indirectly,” she said. “If one or more of these missing houses had charms or spells on them to make them unnoticeable, and you were noticing them regardless, it’s quite impressive. The cumulative effect of the charms would, however, have added up, and when you were distracted by something else, they took effect to make sure you never returned to that line of investigation. But no one actually tried to cast something on you specifically. And I promise we didn’t have anything to do with the monkeys.”

“And that brings us here,” Sherlock said, stopping suddenly and pivoting to face two of the houses. “Number 12, Grimmauld Place.”

John and Mary looked from the door of one house, which had a shining brass number 11 on it, to the next, which had the number 13.

“All right,” said John slowly, “I’m not going to be stupid and ignore everything you’ve just said and say ‘But Sherlock, there’s no house here!’ Even though I very much want to, and there is, in fact, no house here. And I want even more to leave this street and never come back – where are you going, Mary?”

Mary had acquired a blank look on her face and had turned to go back to the main road, leaving the rest of the group behind.

John grabbed her hand and Sherlock darted around to block her path.

“John, what are you doing? We need to go home now, Amanda needs us!”

“And that’s exactly how a Muggle-Repelling Charm works. Let’s deal with this right now,” said Hermione, fishing in her beaded bag/canvas tote. Instead of pulling out a wand or similar magic device, she produced a plain leather wallet, and pulled a strip of folded paper out of it. “Mary, read what’s written here. Hold your pendant in your hand, that might make it easier.”

“Out loud?”

“No, you won’t be able to. Just read it to yourself. Memorize it.”

Trembling, Mary did as she was instructed. She looked up from the paper at the two houses, gasped in shock, and turned to bury her face in John’s shoulder.

Hermione carefully removed the slip from Mary’s clenched fist and gave it to Sherlock, who held it where both he and John could read it. The handwriting was old-fashioned but clear. The Family Seat of the Ancient and Noble House of Black may be found at Number Twelve, Grimmauld Place, London.

Sherlock looked up expectantly, and sure enough, a door, followed by stone front steps, walls and windows, appeared, shouldering its way into existence between numbers Eleven and Thirteen. It looked mostly like the other houses on the street, clean and well-kept, except that the polished silver door knocker was made in the shape of a snake twisted into a knot, and there was no keyhole or letterbox.

Hermione tucked her wallet and the slip of paper back into her bag. “This way, please,” she said briskly, leading them up to the front door. She drew her wand and tapped it on the door, announcing her name. There was a brief pause, then a series of metallic clicks and clanks and the clatter of a chain. The door swung open soundlessly on well-oiled hinges and closed behind them when they stepped through, relocking itself with the appropriate noises. “Sorry about the sound effects,” Hermione said in an embarrassed tone. “They’re a bit old-fashioned, but they were built into the original locks and we can’t get rid of them without rejiggering the entire protection scheme.”

“No, it’s fine,” Sherlock assured her. “Very … atmospheric.”

It seemed like they had stepped back a century in time. As they looked around, old-fashioned gas lights on the walls and a sparkling chandelier overhead lit up to illuminate the entry in which they stood. The space would have been more appropriate to one of the Grand Old Houses of London than to a simple row house. For one thing, there was an entrance to a large parlour with a huge fireplace located in what should have been the house next door. The House of Black also apparently borrowed space from black holes. On the opposite side from the parlour was a formal sitting room; straight ahead was an elaborate grand staircase flanked by a hallway leading back into the more private rooms of the house. A few large portraits hung on the walls. The carpet was a deep, lush green, and the wallpaper bore a soft, abstract pattern of pale green and silver swirls on cream. The colour scheme was carried on into the other rooms visible.

Sherlock didn’t know exactly what he had expected of a magical house, but this wasn’t it. His rooms in Baker Street were more unusual than this. There were a few outré touches, of course. The spindles on the staircase were entwined with carved wooden serpents, and one of them had been brightly painted with red and gold and black stripes to resemble a coral snake. There was an umbrella stand made from the preserved foot of some large humanoid creature with greyish skin and thick toenails. And the figures in the portraits on the walls were moving, shifting in their frames to get a better look at them.

“If you wanted atmosphere,” said Hermione, “You should have seen what this place looked like twenty years ago. It was a total dump. Cobwebs, peeling wallpaper, things with far too many legs scuttling about in the walls, you name it. Classic haunted house style. Smelt bad, too.” She sighed happily as she looked around. “We put a lot of work into renovating it.”

“We?”

“Well, Sirius mostly, and Remus since they were living here, but a lot of us visited and did our bit. It took years. I think Charlie did that,” she said, pointing at the painted spindle. “Said there was far too much Slytherin in the place, even in pastels. So he brightened it up a bit.”

The sound of footsteps on the staircase drew their attention, as two men descended from the upper floors. “Hermione, good to see you again! And who is this you’ve brought to the beautiful House of Black? Tourists? Interior decorators looking for DIY tips?” The man barked a brief laugh at his own joke.

“I told you we’d be coming, or were you so deep in your work that you didn’t hear me?” Hermione said fondly. “Sirius, Remus, I’d like to introduce Sherlock Holmes, Doctor John Watson, and his wife Mary Watson, the investigators that the Ministry let me hire. Sherlock, John and Mary, this is Sirius Black, Head of the Ancient and Noble House of Black, and Remus Lupin, the Steward to the House of Black.”

Sherlock gave the two men his customary quick once-over. The first of the two, obviously the social superior but also good friend of the other, was tall, about Sherlock’s own height, and thin. His features were sharp and aristocratic, handsome if one was given to subjective descriptions. He had black hair shot with strands of silver, worn about shoulder-length but tied back in a tail held with a black ribbon; his skin was fair and his eyes were deep grey. Sherlock would have guessed him to be in his mid- to late forties, but from what Hermione had said earlier, wizards might age at a different rate, so he might well be older than that. His clothing was a mix of magical and non-magical style, Sherlock supposed: black shoes and trousers, a shirt of such a deep blood red that it was almost purple, and a black velvet robe, open down the front and about knee-length, with gold gryphons embroidered on it. He guessed the robe was the magical equivalent of a suit jacket, appropriate for greeting visitors. Aside from the age difference, Sherlock thought this man might almost be a magical mirror version of himself.

The second man was taller than the first by about an inch, but stood slightly stooped, either by age or infirmity. Judging by his face, he was about the same age as his companion, though his features bore the signs of chronic illness, but his hair was pure white. From the colours of his eyebrows and moustache, it had originally been light brown. His eyes were warm brown with flecks of gold. His clothing was non-magical in style but old-fashioned; something John’s father or grandfather might easily have worn, but not so out of date as to attract attention on the street. It might even be considered ‘retro’. He held himself almost the way John had when they first met, the stiffness of an old injury affecting his posture, and was obviously tired. He had a single deep red scratch running down the right side of his face, his throat, and underneath his collar. It was a day or two old, and Sherlock wondered why he hadn’t had it treated, given the efficiency of magical medicine. John would have been all over it if Sherlock had acquired an injury like that. This man was not a magical mirror John – that would be Ducky Mallard – but he obviously filled that role.

There were apparently at least two dogs, quite large, with which the men associated frequently, since traces of a fine black and coarser brown hair clung to their clothing. There was no sign of dog hair on the carpet, so the animals were most likely not allowed in the house.

The man introduced as Sirius Black stepped forward, holding his hand out to Sherlock. “Welcome to the House of Black,” he said formally. “I hope your work will be successful.” After they’d shaken hands, he shook off the air of formality like a dog shaking off the rain. “And now that the boring introductions are over, you can call us Sirius and Remus. Please come upstairs so we can get to know each other a little before the mob starts arriving.”

“You called the Order?” Hermione asked.

“Of course. Everyone wanted to meet the man who’s going to find Harry. And put in their two knuts on where you should look, of course.” He barked another quick laugh. “So I want to get in my two knuts first.”

Sirius led them up the stairs and into an exquisitely appointed drawing room. It was flooded with light from large windows overlooking the street, though Sherlock did not recall such windows existing on the exterior of the building. Magic was going to make observing and deducing a lot more difficult; a great number of things had just moved from the “impossible and therefore eliminated” category of his favourite maxim to “improbable and therefore possibly true”. He was sure there were rules. He just had to learn them.

The wall opposite the entrance to the room was covered floor to ceiling and side to side with an elaborate tapestry which was undoubtedly older than the house was by several hundred years at least. It was handwoven linen, with golden embroidery in swirling lines and lettering that formed an elaborate family tree. At the top were the words THE NOBLE AND MOST ANCIENT HOUSE OF BLACK, and below it: Toujours Pur executed in elaborate stitching.

The wall opposite the windows was occupied by a large fireplace flanked by two ornate, antique glass-fronted cabinets displaying the sort of valuable bric-a-brac a very old family collects. Above the fireplace was a display of heraldic achievement: the escutcheon displayed arms sable with chevron argent, two five-pointed stars argent above and a sword argent beneath; the supporters were hounds, and the motto on the banner below also read Toujours Pur. There was no coronet, helm or crest; apparently the Black family hadn’t moved in the most exalted of circles, assuming the arms were legitimate at all.

The centre of the room was occupied by a collection of chairs and a sofa, with a low table bearing a silver tea set. Fragrant steam rose from the pot. There was plenty of space for everybody to get comfortable, once Mary got over her diffidence about sitting on something that looked like a priceless antique. “Don’t worry about it, Mrs. Watson,” said Sirius, flinging himself carelessly into a chair. “What’s furniture for, if not to be used?”

Hermione acted as hostess, distributing tea and exquisite little cakes as desired. Sirius and Sherlock exchanged measuring looks while the niceties were dealt with. Remus Lupin eyed both of them speculatively over his cup of tea.

“So,” said Sherlock, breaking the silence. “You can give me information about Harry Potter?”

“For what it’s worth. Most of what I have is from after he joined the wizarding world. His school books. His photo album. A clippings file from when he went missing. Search reports on all the places where he wasn’t. I don’t know much about where he would have gone among the Muggles. But if you need anything I have, it’s yours. Information, money for bribes … if you need anybody turned into a frog. Name it.”

Sherlock had the distinct feeling he wasn’t joking.

“You have to understand, Harry is … Harry’s father was my best friend in school. The two of us … we were like brothers. Closer than that, maybe. We would have killed for each other. We would have died for each other. Either way would have been okay. So when James married Lily, I was his Best Man, and when Harry was born, they named me his Godfather. I knew I was never going to have a son of my own already by then and I’d been disowned by my own family – or so I believed at the time – so Harry was all I was ever going to have. I made him my Heir. James agreed … We were blood-bound, the whole nine yards. How anybody could have believed I’d hurt that boy … I loved him.”

“At the age of twenty, you were already convinced you’d never have children.”

“Well … let’s just say Lily and I shared the same tastes. I understand some things are the same in both worlds, Mr. Holmes.”

“And James knew.”

“Of course he did. We shared living quarters for seven years. We all knew everything about each other. I thought we did, anyway, until Peter … But nothing was ever going to come of it, we also both knew that. And there was Lily, of course. That was a love match if I ever saw one. He was happy, and I was content with that. And when they asked me if I wanted to be blood-bound with Harry after he was born … that was more than I ever dreamed of.”

“What’s blood-binding?” asked Hermione. “I don’t think I’ve ever heard of it.”

“Well, you wouldn’t have, necessarily. It’s a Pureblood thing. A form of adoption. For dynastic purposes, mostly, when a line is dying out, or the only option for someone like me – it didn’t mean his parents gave him up, or anything like that. More like I became a third parent to him. So we did the blood-bond, which meant everything I owned would eventually go to him, even if my cousins objected. I didn’t know then that eventually all this,” he said, waving his hand to indicate the house and everything it represented, “would come to me. When we were in our twenties, we were young and poor and fighting for our lives and trying to make it a better world for our boy … It was fantastic, really.”

“Dum vivimus, vivamus,” murmured John.

“Yes, exactly!” replied Sirius with a wide grin. “We crammed all the living we could into every day. We had a year, and then that damned Prophecy … Have you seen that, yet? We’ll have to do that before you go … James and Lily took Harry into hiding, and for a while they made it, but they were betrayed. We were all betrayed.” His good humour evaporated as quickly as it had come. “After that, I think I had less than a few hours with Harry in total. A few letters. I was hoping for so much more, I wanted to give him a home, maybe try to be a father even if I couldn’t be his real father. He was angry at me at the end because I couldn’t take him away from the Dursleys. I didn’t know how bad it was for him there, none of us did, but I should have. I should have, and I failed the one person who meant the most to me. Can you understand that, Mr. Holmes?” He stared at Sherlock, his grey eyes sparkling with unshed tears.

“Yes, Mr. Black. I understand that perfectly.”

“If he’s stayed away all this time, it’s unlikely he’ll ever forgive me, but that doesn’t matter. I just want to know if he’s well, if he’s safe. Help him any way I can, even if it’s only to protect him from a distance. With my magic or with my life, I swear it.”

“You’re that sure that I’m going to find him?”

“I trust Hermione’s judgment. She assures me Harry’s alive. And she’s shown me the reports on you. If anyone can track down someone who disappeared twenty years ago, it’s you.”

“Miss Granger’s confidence is appreciated.”

She smiled at him over her cup. “Anybody that can figure out where the Unplottable Houses are deserves my confidence.”

“Really?” Sirius said with surprise.

“Really. Thirty-seven out of the forty-one,” she said. “And now that I’ve said ‘forty-one’, he’s not going to rest until he’s found the four he missed.”

Sherlock could not deny that – he was already trying to figure out where the ones he’d missed would most likely be hiding.

“There are people who’d want him killed for that, so best keep it quiet,” said Sirius.

“Killed – for houses?” sputtered John.

“Killed because Muggles aren’t supposed to know wizard secrets,” said Sirius. “Some of those houses are owned by the wizarding elite, and now Sherlock can find them. Hell, my parents would have been howling for his head for finding this place.”

“Then it’s a good thing that I’m not exactly non-magical,” said Sherlock. “And killing me wouldn’t help at all in any event,” said Sherlock calmly, as if he discussed his own death with others on a regular basis. Although he did exactly that far too frequently for comfort. “There are Missing House enthusiasts all over the world, trading information about the Missing Houses in every major city. I’m told there’s an entire street in New York City that’s only visible on alternate Tuesdays. I’ve been thinking about going to see it someday.”

“So much for the Secrecy Statutes,” said Remus.

“‘Not exactly non-magical’?” asked Sirius.

“We found out today that Sherlock’s actually a wizard,” Hermione told him. “He had his magic bound when he was a child, that’s why no one knew. And John’s a Squib, so Mary’s an allowed family member under the Statutes. I’ll admit I’m worried about these enthusiasts, but we can deal with that later.”

“A bound wizard. That’s … that’s awful. Something can be done about that, can’t it?”

“Dr. Mallard said the bindings are coming off naturally. Once it’s done, we can register him as a newly discovered Muggleborn, or try to find out if he’s related to one of the known families. I’m sure he is, but proving it is something else.”

“That would explain that, then,” said Remus. “I’m pretty sure he’s a Black.”

“That’s what I thought, but I couldn’t be sure. You can tell?” Hermione asked eagerly.

Remus laid a finger alongside his nose. “We’re still close enough to the full that I haven’t lost the nose yet. There’s something else, too, I can’t quite place it, but definitely a Black. Sirius, look at Sherlock … really look … I think you can see it too. The hair, the shape of the eyes … a bit of the mouth, too. What woman do we know who had eyes and a mouth like that?”

“Bella … her eyes were darker, but …” Sirius breathed out. “And Rod would explain the cheekbones. But then the binding … no, the Ministry wouldn’t have done that. Would they? No, what am I saying, of course they would.”

Sherlock resisted the urge to squirm a bit under their scrutiny. Is this how it feels for other people when I deduce them? No wonder they get upset.

“They would what?” asked John.

“My cousin, Bellatrix Black, married one Rodolphus Lestrange, and both of them became Death Eaters. She was pretty much the worst of a bad lot – she bought into You-Know-Who’s ideology totally. She was captured after his fall while torturing a pair of Aurors into insanity trying to get information. There’s been a persistent rumour that she was pregnant at the time, though she was actually proud of what she did and wouldn’t have tried to plead her belly to avoid Azkaban. But she wasn’t sent to Azkaban immediately after trial, and this would explain why. The last thing the Ministry would have wanted was for there to be a male heir to the Lestrange Family, but they wouldn’t kill an innocent baby. Not even Crouch would have done that. It would have been too dangerous to just put him in an orphanage and treat him as a Muggleborn – that’s how You-Know-Who got his start, after all. But if they bound his magic so he’d never be more than a Muggle and then dumped him … Merlin, that’s ugly.”

“Beyond ugly,” agreed Remus. “But if all that’s true, then he could lay claim to the Lestrange estate, and he’d be, what, second in line for Black after Harry? Teddy wouldn’t mind being pushed back to third, I think.”

“There will have to be some research done, of course, but if this turns out to be the truth, I’ll be happy to welcome you to the family, Sherlock. If it is true, unfortunately, it means your mother was batshit crazy and your father wasn’t much better, but I won’t hold that against you. We’re all a little mad here.”

“Yes, perhaps we can deal with that later? I really would like to look over the evidence regarding Harry Potter before we’re invaded by dinner guests,” Sherlock said. The unexpected resemblance between himself and some of Sirius’ family members was interesting, but not exactly important at the moment.

“Of course, of course. Terribly sorry, I’ve been distractible ever since Azkaban. Where would you like to begin?”

“There have been multiple references to a Prophecy. Do you have a copy I could read?”

“Better than that, I’ll show you. We have a preserved copy of the original.”

“A video recording? From thirty years ago?”

“More like thirty-five, and it’s not video. It’s something better. Come on!” Sirius leapt energetically to his feet and led the way out of the room and up another flight of stairs. “I set up a bedroom for Harry here when I thought he would be coming to live with me. When his things were retrieved from Privet Drive the Christmas after he went missing, I unpacked them and put them away here.” He opened the door to a large bedroom, decorated in opulent scarlet and red fabrics and furnishings against cream walls. The bed was a four-poster with red and gold brocade curtains, the wardrobe was oak, and a matching glass-fronted bookcase stood next to an oak desk with an upholstered chair. Offsetting the antique furnishings were what appeared to be framed sports posters and personal photographs on the walls. The images on the posters and photos, however, were moving, just like the pictures in the books they had bought earlier.

“He was gone six months before you went to get his belongings?” Sherlock asked Hermione.

“How did you know I –”

“Pushpins,” Sherlock said shortly. “The pins on his corkboard were arranged the same way you rearranged the ones in our office. Habit, I’d guess.”

Hermione simply nodded. “The room had some pretty heavy protections on it,” she said. “But you knew that. It turned out it was only accessible by Apparition – and then only by people who had been there and Harry knew and trusted. Even the Headmaster couldn’t get in, which if I’d thought about it at the time … anyway, Fred and George and Ron Weasley were the only ones who ever were actually in Harry’s room, and of course they were all at Hogwarts and it’s impossible to Apparate from there, so we had to wait until Christmas break to do it. With everything else that was going on then, we almost didn’t get to do it at all, and Ron didn’t want to go so Fred brought me side-along. Harry trusted me enough to get through; George was trying to side-along an Auror and they got bounced hard.”

“What exactly is Apparition?” asked John, who was used to asking questions so Sherlock wouldn’t have to.

“Allow me to demonstrate, it may be easier than explaining,” Hermione said. She got up and moved to one corner of the room. “John, if you would watch me, Sherlock, you watch that corner over there. Mary, take your pick.” She made a step forward with a graceful twirl and vanished, reappearing in the corner diagonally across the room next to the bookcase to finish her twirl. A loud CRACK! accompanied her translocation.

“Teleportation! Amazing!” said John.

“We call it Apparition. The term predates the coining of the word ‘teleportation’ by centuries,” said Hermione, primly. “Most wizarding homes have spells in place to prevent people from Apparating into them directly unless you’re known and trusted, for obvious reasons. Good manners – and personal safety – require a person to Apparate in at a distance and then approach on foot so that you can be seen.”

“As you did when you came to visit us in Baker Street,” said Sherlock.

“Yes; there’s an alley down the way that isn’t covered by CCTV cameras, so we just Apparated there. We could very easily have Apparated into your office directly today, but that would have been rude.”

“And probably would have got at least one of you shot,” said John.

“Both,” said Mary, calmly.

“Yes, well. You see why it isn’t done. Though we should probably put some charms on your flat and office just in case. We didn’t think the Dursleys would permit us to come in, so we waited until they were out of the house and then Apparated into Harry’s room directly so they would never know we’d been there.” She paused to think for a moment. “I’m fairly sure nobody ever taught Harry about anti-Apparition jinxes, so that means he made them up on his own. And he made one the Aurors and Dumbledore couldn’t get through. That is beyond impressive. I really wish I had his notes.”

“I may be able to help you there,” Sherlock mused, looking over the bookcase. “Sirius, may I?”

“Of course.” Sirius tapped the bookcase with his wand, and the glass door opened.

Sherlock leaned down and removed a notebook from one of the lower shelves. Without opening it or even looking at the front cover, he handed it to Hermione. “I believe this is what you’re looking for.”

Hermione looked rather dubiously at the front of the book, which proclaimed itself to be Dudley Dursley’s maths notes, but then flipped it open to look inside at a random page. She uttered an undignified squeak and clutched the book to her chest. “This is it exactly! Thank you, you saved me so much time!” She was practically vibrating with eagerness to start reviewing the notebook.

Sirius gaped at her, and then at Sherlock. “How did you know that was there? How did you know what it was ? You didn’t even look at it!”

John laughed whole-heartedly. “This is Sherlock Holmes. It’s what he does. It’s why you wanted him in the first place. Go ahead, show them how it works.”

Hermione looked up from the notebook, smiling, her cheeks pink. “Oh do, please. It really has to be seen to be believed!”

Sherlock sighed. He wasn’t at all sure how to take this. It was one thing when everybody (except John) doubted and he had to prove it. This felt more like being part of a dog-and-pony show, and he wasn’t sure if he was the dog or the one-trick pony. Still, Sirius and Remus probably needed convincing. Once he started, as usual, he was swept away on the tide of his deductions. “It was obvious from the nature of the rune layouts that there would have to be preliminary designs and scratch work made, probably in a workbook of some kind. The desk contained clues to show how the runes had been made – bits of wrapping tissue and pencils worn down to the nub to make home-made transfer paper, and a pen with no ink used as a stylus to mark them in the paint. Possibly the scratch work was destroyed afterwards, but I thought it unlikely – people usually like to keep that sort of work for future reference. Therefore it was most likely removed by whoever cleaned out the rooms afterwards – including the compulsive pushpin organizer. She also accidentally dropped the calendar behind the desk. You really should have retrieved that, by the way.”

Hermione shrugged. “It was just a calendar, and we were in a rush.”

“Still. It provided me with the exact dates of Harry’s residence in that room up to the day of his disappearance, a sample of his handwriting, and an indication that he expected to leave the Dursley’s residence on 1 September – all of which indicated that he attended a boarding school, where they had some sort of antiquities or fantasy-fiction enthusiast’s club that taught things like how to cut quills, make oak-gall ink, and write spells in Tolkien’s runes, as evidenced by his hiding space. At least that’s what I believed at the time. It was only later that it became apparent that he expected the spells to actually work. I assume ‘alohomora’ and ‘colloportus’ are important given their prominence on the frame of the door.”

Hermione started to answer, but Sherlock held his hand up to forestall her. “Later. Dudley Dursley told us that Harry would be picked up suddenly during the summer, so he probably kept his things packed to leave at a moment’s notice. So his notebook was already packed along with his other school books, and Hermione never saw it and wouldn’t have known to look for it since she hadn’t noticed the runes or realized their significance.”

“That room was filled with runes,” John said. “You didn’t see them?”

“We didn’t notice them until I found that first set and we started looking for them,” Sherlock reminded him. “Most of them just looked like random scratches in the paint at first.” Though he was beginning to think now that they never would have found any of them if it hadn’t been him looking for them.

“That’s not an excuse; I should have been looking,” Hermione said gloomily.

“You were just a student, not an Auror yet,” said Sherlock. “You’d only just taught him the basics. You had no reason to believe he’d have been able to do anything that extensive, am I correct?”

“You’re correct, but still … it hurts to know I’d underestimated him so badly.”

“None of us knew,” said Dean. “We were all in the same classes, Hermione, and there just wasn’t any indication he was that good. Decent in Charms, struggled with Transfiguration, and Potions we won’t talk about. Except in Defense, of course, there he was brilliant.”

“That’s what should have told me I was underestimating him,” Hermione insisted. “Defense was the all-round class that brought everything else together. There’s no way he should have done that well at Defense without being better at everything else than he was letting on. Even Potions.”

“In any event, it was Hermione and Fred and George Weasley who retrieved Harry’s belongings, but Sirius who unpacked them and put them in the case here. He also didn’t know there was anything unusual among them. Look at the arrangement of the books on the shelves: textbooks, organized by subject, on the top two shelves. Miscellaneous books, presumably not textbooks but acquired as gifts or because of personal interests, on the next shelf. One gap here, where the runes book was put originally before Hermione retrieved it and returned it to the school library. The next two shelves down are filled with binders, all the same type and colour and fairly expensive, organizing class notes, again by subject and year.”

“I gave him those,” said Hermione. “Harry and Ron both had atrocious stacks of loose notes, and it was amazing that they managed to find anything at all sometimes. I punched holes in my parchment sheets and put them in binders to keep things organized. When I went home for Christmas break the first year, I bought binder sets for both of them. Harry used his, Ron didn’t. So after that I just bought a set for Harry at the beginning of every year. Ron teased him about giving in to my nagging, but I think Harry really appreciated it.”

“I’m sure he did. He wouldn’t have kept up with the system otherwise.” It wasn’t just a reassurance. It was the same system that he had automatically used in school and still used to organize notes on various subjects, both on paper and in his Mind Palace. He wondered just how much of Harry had been retained on an unconscious level.

“So the random items, journals and logs and project notes that didn’t fit any of the categories, went on the bottom shelf. Harry didn’t have a spare binder that last summer, and no money with which to acquire one, so he took a notebook discarded by Dudley, removed Dudley’s notes – not many, given by the scant number of pages torn out – and used that for his runes workbook. It’s a standard spiral bound notebook, doesn’t match anything else in the shelf, and stuck out like a sore thumb. The tissue paper was neatly folded and stuck in the back, but the edges are clearly visible. It couldn’t be anything else.”

Sirius nodded. “That was … amazing. Now I know you’ll find him. Well. Shall we look at the Prophecy now?”

He sat down at the desk and opened a lower drawer, from which he removed a stone bowl with a cover, both heavily decorated with runes incised into the stone.

Sherlock recognized some of them as bindrunes, but there were also Greek letters and Egyptian hieroglyphs worked in, and things he didn’t recognize at all. Clearly the art of runic engraving went far beyond what Harry had learned.

Sirius placed the bowl squarely in the centre of the desk and removed the lid. The bowl was about half full with a swirling whitish-silver substance that might have been liquid or might have been clouds trapped inside. A silvery light shone from the substance.

“This is a Pensieve,” Sirius said. “It’s a device for displaying or reviewing preserved memories. This one belonged to Professor Dumbledore; he gave it and a library of memories to me shortly before his death. It’s been vital to our efforts since.”

“You can preserve memories directly?” Sherlock was frankly astounded – he had never expected something like that to make it from the ‘impossible’ to ‘improbable’ category. John was simply nodding – maybe this was a concept he’d run across in his fiction.

“How does it work?”

“First you take a memory – here, I’ll show you one from this afternoon, so you can tell it’s not a fake.” Sirius drew his wand from his sleeve and touched the tip to his temple. When he drew it away, there was a silvery gossamer strand clinging to it. “And then we put it in the Pensieve, so.” He dropped it into the bowl, where it merged with the silvery fluid. “And before you ask, yes, I can get it out again, and no, it’s not gone from my mind – it’s just a copy. And now we can display it.” He prodded the silvery substance with the tip of his wand.

A ghostly silver staircase rose from the liquid, with two people standing at the top landing and five at the bottom. The view was from the top of the stairs, looking down. Hermione’s voice came faintly at first, but then the volume increased as Sirius poked the silver liquid again.

“You should have seen what this place looked like twenty years ago. It was a total dump. Cobwebs, peeling wallpaper, things with too many legs scuttling about in the walls, you name it. Classic haunted house style. Smelt bad, too. We put a lot of work into renovating it.”

“We?”

“Well, Sirius mostly, and Remus since they were living here, but a lot of us visited and did our bit. It took years. I think Charlie did that. Said there was far too much Slytherin in the place, even in pastels. So he brightened it up a bit.”

The two figures at the top of the stair started their descent. “Hermione, good to see you again! And who is this you’ve brought to the beautiful House of Black? Tourists? Interior decorators looking for DIY tips?”

“I told you we’d be coming, or were you so deep in your work that you didn’t hear me? Sirius, Remus, I’d like to introduce Sherlock Holmes, Doctor John Watson, and his wife Mary Watson, the investigators that the Ministry let me hire. Sherlock, John and Mary, this is Sirius Black, Head of the Ancient and Noble House of Black, and Remus Lupin, the Steward to the House of Black.”

The little figure of Sirius stepped forward, holding its hand out to the little Sherlock. “Welcome to the House of Black. I hope your work will be successful. And now that the boring introductions are over, you can call us Sirius and Remus. Please come upstairs so we can get to know each other a little before the mob starts arriving.” The figures and the silver staircase sank into the bowl and dissolved.

“There, see how it works? If you like, Hermione could show you one where I wasn’t present, but you were.”

“No, no, maybe later. This is remarkable. It’s like a shared Mind Palace. Can anyone work this? Could you, for example, display a memory of mine where none of you were present? Or one of John’s, or Mary’s?”

Hermione chewed her lip. “I don’t know. I don’t believe it’s ever been tested with squibs or non-magicals.”

“I’ll pass, thanks,” said John. “Far too many wands near my head today for comfort.”

“And Mary’s too important to us to use as a guinea pig,” said Sherlock. “Though the experiment should be done eventually. What about me?”

“I’d say you’re even more important. But we’re going to have to know if we can use it with you sooner or later, so let’s give it a try. Why don’t you switch places with Sirius, and I’ll try to pull a memory. Close your eyes, and think of something you can remember clearly – maybe something important that John and Mary can verify? Just a few seconds worth, bring it to the front of your mind, and … there!”

Hermione’s wand tip touched his temple, and then Sherlock felt a distinctly odd pulling sensation. He opened his eyes in time to see a glowing filament of memory drop into the bowl.

“That must have been a strong one. It was very bright.”

“There were several I could have used, but this one … had the least blood in it.”

“And I’m sure we all appreciate that. Let’s see it, then.” She poked the surface of the cloud with her wand.

Instead of a tiny silver display, a whole room burst into presence around them, filled with light and colour and music. Sirius, Remus and Dean whipped out their wands and turned to face what might have been an unexpected attack. Instead, it was the reception hall at John and Mary’s wedding. The happy couple in their wedding clothes had just finished a dip, and everyone around them clapped and cheered, while Sherlock, in his formal suit, stood on a low stage with his violin and drew out the last note of the waltz he had written just for them. The group of wizards stood in the clear space on the dance floor between the stage and the bridal couple.

“Oh. My. God,” Hermione breathed out, trying to look around herself in all directions at once.

“This wasn’t supposed to happen?” asked Mary.

“No, it’s not!” replied Sirius, raising his voice to be heard over the cheering crowd. “This is what happens when you go into the memory, not when it displays!”

Nobody in the crowd seemed to notice the seven new arrivals. John raised a finger and poked at his formally-clad doppelganger, only to find himself shifted away slightly before making contact.

Dean stopped his hand before he could try again. “You can’t move or touch anything in a memory. If you try, it just moves you further away from it, and enough of that can make you dizzy. It’s different if you move around on your own.”

Up on the stage, memory-Sherlock put down the instrument and took up a buttonhole flower that was lying on the music stand and flung it out into the audience. A pretty, dark-haired young woman in a lilac bridesmaid dress caught it. Memory-John, meanwhile, had pulled Mary upright again and waved his thanks to Sherlock.

Sherlock stepped over to the microphone on the stage near him. “Ladies and gentlemen, just, er, one last thing before the evening begins properly. Apologies for earlier. A crisis arose and was dealt with.” He drew in a breath. “More importantly, however, today we saw two people make vows. I’ve never made a vow in my life, and after tonight I never will again. So, here in front of you all, my first and last vow. Mary and John: whatever it takes, whatever happens, from now on I swear I will always be there, always, for all three of you.” He hesitated and stuttered. “Er, I’m sorry, I mean, I mean two of you. All two of you. Both of you, in fact. I’ve just miscounted.”

Memory-John and Mary exchanged slightly worried looks, while the real John and Mary burst out laughing.

Memory-Sherlock continued. “Anyway, it’s time for dancing.” He spoke over his shoulder to the DJ behind him on the stage. “Play the music again, please, thank you.”

And the ballroom disappeared, leaving the group standing in Harry’s bedroom again. Remus, still on alert, was threatening the four-poster bed while Sirius brandished his wand at the bookcase. They recovered and put their wands away when they realized there was no actual threat.

“Was that … not good?” asked Sherlock. “I was trying to remember that as clearly as possible.”

“You did that and then some,” said Hermione. “And thank you very much for not remembering anything with blood.”

“You said something important that John and Mary could identify. Many of the important memories with all three of us are far less pleasant than that one. Though I hadn’t been aware of just how … awkward that whole thing was.”

“Yeah, you spent that whole day being the King of Awkward,” said John. “I really should have known what was going to happen when I asked you to be my Best Man.”

“Yes, you should have,” agreed Mary. “But you’ve got to admit, it was probably the least boring Best Man speech in history.”

“And we’re going to have to give you a little lesson on the subject of vows later, Sherlock,” said Sirius. “They may not mean much to Muggles, but for a wizard … That was very dangerous, what you did. We don’t make vows often, and it’s not just a cultural thing. They’re binding. Even unto death, sometimes. Or beyond. Good thing you didn’t repeat that ‘always’ a third time or it could bring you back as a ghost. Or worse.”

“There’s worse?” asked John.

“Yes, and don’t ask, or we’ll be here all night,” said Sirius. He returned to the desk and used his wand to fish the glowing thread of Sherlock’s memory out of the bowl. “Let me just put this back where it belongs ….”

Sherlock allowed him to touch his temple with the wand, and felt a sort of slithery sensation inside his head as the thread returned to its proper place.

“And now, ladies and gentlemen, the main event … although regrettably less spectacular than the opening act … the Prophecy!”

He opened the top drawer of the desk, which was full of small vials similar to the ones Hermione had put potions in. Each was full of silvery fluid, like the Pensieve. Gossamer threads snaked about inside the vials. Sirius selected one from the front row and poured it into the stone bowl, then poked it.

A woman’s figure rose out of it, draped in gypsy-like shawls, wearing a multitude of bracelets and rings. She had glasses that magnified her eyes to enormous size. Her jaw worked spastically for a moment, and then she spoke in harsh, hoarse tones.

“THE ONE WITH THE POWER TO VANQUISH THE DARK LORD APPROACHES ... BORN TO THOSE WHO HAVE THRICE DEFIED HIM, BORN AS THE SEVENTH MONTH DIES ... AND THE DARK LORD WILL MARK HIM AS HIS EQUAL, BUT HE WILL HAVE POWER THE DARK LORD KNOWS NOT ... AND EITHER MUST DIE AT THE HAND OF THE OTHER FOR NEITHER CAN LIVE WHILE THE OTHER SURVIVES ... THE ONE WITH THE POWER TO VANQUISH THE DARK LORD WILL BE BORN AS THE SEVENTH MONTH DIES ...”

The figure sank back into the silver mass and vanished.

“Need me to show it again?” asked Sirius. “Or we could go directly into the memory for more detail.”

“No, that will be quite sufficient,” said Sherlock slowly. “That was … extraordinary. And worryingly unclear. You say everybody believes this is about Harry Potter and Voldemort?”

“You see what I mean about divination being a very woolly discipline,” said Hermione. “No specificity at all, and it can only be fully understood in retrospect, which doesn’t help us much here and now. The prophecy was delivered by Sibyl Trelawney during her job interview for the Divinations post at Hogwarts, to Headmaster Dumbledore, whose memory this is. Dumbledore believed it related to either of two babies who were in utero at the time with due dates at the end of July, Harry Potter or Neville Longbottom. Neville was born on the 30th of July, Harry the next day on the 31st. Over a year later, Harry was ‘marked’ by Voldemort when they met for the first time. Voldemort’s body was destroyed and Harry was left with a curse scar on his forehead.”

“But that wasn’t enough to satisfy the Prophecy.”

“No, that just established the opening conditions. Dumbledore, and most everybody else, believed that the prophecy means only Harry can kill Voldemort for good, which is why he keeps coming back. By the same token, only Voldemort can kill Harry for good, which is why everyone believes he’s still alive. Only when the two of them meet again, at full power, will one of them finally kill the other. Although it could also be a mutual take-out, I suppose. I think that’s what Dumbledore was expecting, actually. But he anticipated having some time to teach Harry the more advanced combat magics once he’d come to full power. Nobody foresaw a situation like this. Dumbledore dead, Harry missing and probably untrained, and Voldemort coming back again and again to spread terror.”

“Asking this Trelawney woman for details hasn’t helped?”

“She doesn’t even remember she gave the Prophecy in the first place. This,” she said, gesturing at the bottle where Sirius had replaced the memory, “is all we have to go on. Well, that and you.”

“And me,” Sherlock agreed sourly. There were a lot of things about his life that were now becoming clearer, and he was not happy about any of it. Except for the not being dead part; he was quite happy with that. He looked at the racks of shimmering memories. “Is there anything in those that might help?”

“Honestly? I don’t know. You can look at anything you think might be useful, of course. Some of those are memories that Dumbledore left for Harry to see; I’ve looked at them, they’re all about Voldemort as a student and a young man. A Dark Lord in training, if you will. Those of us who know how to extract memories can give you relevant ones that you can review whenever you want. We’ve also been using the Pensieve as an espionage tool. They’re ridiculously rare and expensive, and we don’t think You-Know-Who has one, so this one gave us a real tactical advantage. Made it much easier to get reports from our inside agent. He could send us the exact details of Death Eater activities just by giving us memories of what went on, at least as far as he was involved. If he saw documents, he just read them and then saved those memories. Of course we had to be careful what we did with them so as not to give him away.”

“An embedded Enigma, complete with your own Coventry problem. Elegant. But you’ve lost the agent now?”

Hermione nodded sadly. “We lost Severus two years ago. He never came back from his last meeting, so of course we don’t know what happened. The majority of those vials are his memories – I’ve seen most of those too, but I might have missed something, and of course it’s all out of date now. And there’s one set of memories that he left in a sealed vial that only Harry can open. No idea what’s in there, because he’s dead and his portrait can’t tell us.”

“I never liked Severus,” said Sirius, “but I wouldn’t wish a death so horrible that it traumatizes a portrait on anyone.”

“How does a portrait talk? After a person is dead? I’m not getting it,” said John.

“Is it similar to the moving pictures in the books?” asked Sherlock.

“Sort of. The pictures are basically a recording of a short period of time, with limited interaction – sort of like a computer gif, if you could interact with it. They keep recycling through the same image and don’t retain any memory of their interactions. A portrait is more of an echo of a person; their memory and personality, but not their soul. They’re fully interactive and retain memories from those interactions. How much is retained from the subject largely depends on the strength of will of the person depicted, and the skill of the portrait artist. We hired the best artist currently practicing, and Severus certainly had strength of will, but the most his portrait does is blink. If he was a living person, I’d say he was in a coma.”

“Is his portrait here? Could we see it?” asked John.

“Idea?” said Sherlock.

“Maybe. Don’t want to get hopes up if I’m wrong.”

“Of course, he’s in the portrait gallery – we were hoping being with others would wake him up, even if only to yell at them for being dunderheads.”

The portrait gallery was on the same floor as the drawing room with the tapestry. They could hear the chatter of portraits talking to each other as they approached; it had much the same sound as a cocktail party in full swing. Most of the portraits fell silent as they entered, craning their necks or in some cases moving to adjacent frames to get a better look at the strangers. Hermione led them over to a portrait that had a single figure in it, apparently resting.

Severus Snape had not been an attractive man in life, and the portrait artist had not flattered him – the less the portrait was true to the subject, the greater the chance it would not wake. He looked somewhat older than Sirius, possibly in his mid-fifties, judging by the frown lines on his sallow face and streaks of white in his ebony hair. His nose was hawk-like and his lips thin and pinched. His clothing was black except for a few touches of green on the cuffs and lapels of his robe.

John observed him as if he were a patient – he looked like he was asleep, but his breathing was irregular and the tips of his fingers twitched occasionally. His eyes were definitely blinking irregularly. Fast, fast slow fast fast, fast slow slow fast, slow slow … “Oh God,” John whispered, and whisked his pen and notebook out of his jacket pocket. He wrote down the series of blinks as dots and dashes until the sequence started to repeat.

“What’s … oh no,” said Hermione, pressing her hand to her mouth as she recognized the code, and the sequence.

John decoded it rapidly, ripped off the page and handed it to Sirius.

E L P M E S O S

S O S H E L P M E S O S

S O S

“He’s in there. God help him, he’s in there.”