When John arrived at St. Bart’s, the bodies of both Dursleys were laid out, still clothed and with plastic baggies over their hands, in the morgue room reserved for police investigations. The pieces of bloody carpet had been removed and bagged so they could be gone over for trace evidence, though there was just so much blood on them that it would take a real effort to find anything else.

Molly Hooper was bustling about laying out the equipment trays and preparing stacks of evidence bags and sample dishes while she waited for the arrival of the “official” police medical examiner. Regulations required two for suspected homicides, which this most definitely was. While Molly was primarily employed by St. Bart’s, she also had the necessary credentials for CID, as long as one of the police pathologists worked with her. This worked out well for everybody, since Bart’s had its own lab facilities and could get fast test results.

“Oh, John, hi!” said Molly as he pushed his way through the double doors. “Is this one of Sherlock’s, then? Silly me, of course it is. Such unusual murders, and you here … is he going to be coming along?” She glanced past John, eager to see if a tall silhouette was just outside the doors.

“He’ll be here in a bit. He’s doing some canvassing work, if you can believe it. Sent me ahead to give you a hand if you want.”

“And pick my brains and read all my notes and then tell me what I missed. I know how it works.”

“I kind of expected you’d already be elbows deep in Vernon there.”

“Be kind, John. The poor man can’t defend himself.”

“Yeah, well, from what we found at his house, he may not have been a very nice man at all.”

“Doesn’t matter. No matter how … not nice … he may have been, he didn’t deserve this. Nobody deserves this.” She gestured at the table where the body was covered with a plastic sheet – a fabric one would have been ruined in seconds and probably stuck to the body.

John felt properly chastened. Molly was one of the nicest, most mild-mannered people he knew, but she was a staunch defender of the dead. Yes, she gave Sherlock body parts to experiment with – but only from corpses that had been donated specifically for study; St. Bart’s being a teaching hospital, there were actually a fair number of those. Anybody else, no, no matter how interesting the detective might find them. And right now, she was perfectly correct. “Sorry. So what are you waiting for?”

“Dr. Patel. Even with traffic from the Yard, he should have been here half an hour ago, and I’m beginning to get wor – Oh!”

The door swung open, but the person who entered was definitely not someone who would have been named Patel. He was a short man, fair-skinned and with sandy blonde hair a shade lighter than John’s own liberally mixed with white, and about thirty years older – he was slightly stooped but still moved well, wore oval bifocals and a comfortable, casual suit. John could see himself becoming this man as he aged, assuming he didn’t get himself killed chasing after Sherlock. He’d draw the line at the bowtie, though.

“Dr. Mallard!” Molly gasped in pleased surprise. “It’s so good to see you again! I thought you’d retired.”

“No, only semi-retired, my dear. I still get to pull rank on the really interesting cases. Which is why I’m here and Dr. Patel isn’t. Will you introduce me to your handsome companion?”

“Oh, I’m sorry – Dr. Mallard, this is Dr. Watson – he does consulting with the Yard sometimes. On the, um, ‘really interesting cases’.”

“Pleased to meet you then – I’m surprised we haven’t run into each other before,” said Dr. Mallard, reaching out a hand for John to shake. “Was it Afghanistan or Iraq? I trust you’ve recovered from your injury?”

John let out a delighted laugh. “You know, you’re the second person that’s started a conversation that way. It was Afghanistan, actually, but a few years ago now. What, um, what tipped you off?”

“Oh, your hairstyle, your stance, even your clothing, the choice of colour, says ‘former military’. You’re here, and Molly said ‘Doctor’, so that means RAMC or possibly an embedded medic in the Army. You’ve got the alertness – the situational awareness – that says you were in an active theatre, possibly support for the front lines. No rear echelon hospital for you, so regular Army it was. No tan, but your skin still shows the effect of the sun – that takes a long time to leave you. Afghanistan or Iraq, a few years ago. Given your age, you’d probably still be in the service by choice – likely made Major at least by now if you were halfway competent – which means you were invalided out with a serious injury with lasting complications that affected your skills, though it wasn’t crippling – my sympathies for that, by the way. I spent some time in Afghanistan myself, and I fear my generation’s effort only made things worse for yours. There’s something about Afghanistan that means whatever we do there is the wrong thing. You seem to have adjusted since coming home. Whatever consulting work you’ve been doing, it seems to have done well for you – it’s kept you fit and active and maintained your alertness. You’re not a lazy man. Boredom would not suit you. Married, so you’re here in a professional capacity and not hitting on Dr. Hooper – or you’d better not be, anyway – she has dangerous friends.” He cocked his head, eyes twinkling. “So, how’d I do, Dr. Watson?”

“Simply marvellous. And please, call me John. No, I’m not hitting on Molly, I’ve known her for years and while she is a wonderful woman, my wife would kill me if I even thought about that. Molly and I have a mutual dangerous friend who does much the same thing as you just did – I’d like to get you together and watch you deduce each other while we just sit around in admiration.”

“Until they get bored and start deducing us,” said Molly. “That – that never ends well. For me, anyway. But you could also have just seen John’s blog – you could have got everything from that.”

“Why would I have read his blog before I met him?” asked Dr. Mallard.

“’Interesting cases’ and all.”

“Hm. Sounds like I’ll have to look at it. But for now, we do have an interesting case immediately to hand. Shall we, Molly? And Dr. Watson, I assume you’ll be observing as part of your consultancy?”

“It’s why I’m here, yes. If there’s anything I can do to help you, let me know. I’m not a forensics specialist, but I observed the state of the bodies in situ, and I’ve had more than a little practical experience with this sort of thing recently.”

“Very well. Let’s robe up and get started.”

An hour later, the three were deep in the middle of the autopsy of Vernon Dursley; he’d been photographed head to toe and then his clothing carefully cut free from his body and bagged for further examination. Sherlock had been correct – the slash wound that killed him went down several inches below his belt line, yet the belt, trousers and pants were undamaged. Dr. Mallard pursed his lips over that, but did not comment. Molly was checking the hands to see if there were skin scrapings beneath the nails (there weren’t), when suddenly there was a squelching noise and rather a nasty stink filled the room.

“What, sphincters release now?” gasped John as Molly cranked up the ventilation. “That should have happened at TOD, not … seven hours later!” he finished, looking at his watch.

“I’ll just take samples of all that,” said Molly. “Fortunately we’re almost at the point where we can wash him off anyway.”

Shortly afterwards, the air was clear and the search of the body for trace evidence was complete. Molly took samples of the tissues which had been slashed to see if there was any damage from heat, radiation, or anything else that might indicate the wound was more than a simple cut, the body was washed, and the wash water run through a strainer to collect any trace particles they had missed.

John eyed the clock. It was nearing five, Sherlock hadn’t arrived, and the work on Petunia Dursley hadn’t even been started yet. Ordinarily there would have been a second team working on her, but somebody in authority had decided that Dr. Mallard – who had by now decided that sharing an autopsy made one friends and instructed John to call him “Ducky” – and Molly should do both of them.

“Will you be okay with putting in a little overtime, Molly?” asked Ducky. “I’d rather get at least the forensic exam done on her tonight – we can do the full medicals on both of them tomorrow. What do you think?”

“Overtime is good. I’ll just get some coffees and we can take a break before starting on her. John, will you be staying for this one?”

“I’d like to, if you don’t mind, and if you could grab me a tea while you’re going for coffee, I’d be grateful.”

“Sure. Thanks for not just assuming I’d – just thanks.”

“Yeah, that’s the tall rude berk that makes those assumptions. I’m the short polite one.”

After the break, they had changed into fresh scrubs, gowns, and gloves, when Sherlock barged in. “How are you doing with the bodies, John? Tell me you’ve got something interesting – I’ve just spent the most boring hours of my life interviewing suburbanites.”

Molly hastily introduced Sherlock to Ducky and hoped her action would not cause the world to end in the next week or so. You never knew, with Sherlock. Or Ducky, for that matter. Fortunately Sherlock seemed to be more interested in the corpses than in the pathologist. Sherlock was quite interested to hear that the odd rigidity of Vernon’s body had relaxed, and put on gloves to poke him a bit.

“Get anything interesting from the suburbanites?” John asked.

“Only one of the neighbours had lived there long enough to remember our missing person,” said Sherlock distractedly as he tested the flexibility of Vernon’s joints – not much, as he was now in full rigor, but actually better than he was earlier in the day. “Seems he was definitely a neglected child, also used as a commodity – the uncle arranged ‘odd jobs’ for him to do for neighbours, then pocketed the cash. The family didn’t need the money. He apparently just did it to be cruel. Mrs. Sheffield said she used to hire the boy to do garden work just so she could get a good meal into him occasionally. Didn’t blame him at all for running away – probably the best thing for him – she saw the uncle trying to strangle him in the front garden. He got loose and walked away before she could call the police about it. That was apparently the last time anybody ever saw him.”

“Would she recognize him if she saw him again? I know it’s been years, but –”

“No, more’s the pity,” said Sherlock, looking over to the group by Petunia’s autopsy table. “She’s gone blind – diabetes. Told me all about it ad nauseam. Got a good description of what he looked like then – short and thin, small for his age – my guess is undernourishment – dark hair, green eyes, glasses – description could fit hundreds of boys – fortunately he had a rather noticeable zigzag scar to serve as an identifying mark –”

“Yes, well, could we get on with this now, and maybe you could discuss that at the pub later?” asked Ducky. “It’s waited twenty years, I’m sure it can wait a little longer.”

Sherlock looked at Ducky evenly for a moment. “I’m sure it can.” He turned back to Vernon’s body and looked down at him. “I’m beginning to really not like you, Mr. Dursley. Probably a good thing you’re already dead.” He pulled the plastic sheet up to cover the corpulent man before crossing to the other table. “Very well, Doctor. What do you make of these very curious knots on our female victim? Found the ends of the cords yet?”

Despite much searching, none of them could find the ends of the cords binding Petunia Dursley. Ducky eventually decided, regretfully, that he would have to take a scalpel to them. “Doubtless the end will pop out the minute I cut it,” he said as he applied the surgical steel to the silken cords just between the pinioned ankles. He was wrong – the elaborately knotted cord disappeared entirely, as if it had never been. “Oh blast!”

“What the hell happened?” asked John, inspecting the places where the cords had left impressions and bruises on the woman’s bony ankles. He glanced up at Sherlock, who had gone totally still as he tried to process something completely unexpected.

“Did that just – turn into dust?” asked Molly, peering over Ducky’s shoulder. The doctor was as frozen in position as Sherlock, his scalpel still held in mid-air.

“I … don’t know,” the doctor said slowly. “Get me some tape. If there are any particles maybe we can pick them up off her skin and trousers. Don’t move too fast, we don’t want air currents to move them around.”

There were no particles to pick up with the tape, however. The four of them stared at the other cord around Petunia’s wrists, wondering if that, too, was just going to disappear.

“I wouldn’t recommend cutting that,” said John quietly. “Let’s see if we can just work it off her hands. It’s not like we have to worry about hurting her.”

In the end, they had to dislocate one of the victim’s thumbs in order to get a single loop of the cord to slide over her hand, but as John said, she wasn’t going to feel it. Once the first loop was off, the rest of it came loose enough to slide off in a single knotted mass.

Sherlock and John attempted to straighten it out and find the ends while Ducky and Molly began their work on the corpse. “Attempted” turned out to be the operative word. When they were done, they had a single long loop with no ends and one impossible knot in it. They both went over it, John with his sensitive surgeon’s fingers and Sherlock with his magnifying glass, trying to find a place where the ends might have been spliced together. They couldn’t locate one.

“This,” said Sherlock slowly, “is quite extraordinary. It can’t exist – it shouldn’t exist, rather, but it does.”

“Since it clearly does exist, there must be an explanation for it,” said John, reasonably.

“This is at least the fourth – maybe the fifth – extraordinary element in this case. Where there are so many gathered together, they must be related. But how? John, you’re the science-fiction aficionado – how would you explain this in a story?”

“Look, I like reading the stuff – I don’t know enough to write it.”

Sherlock picked up and coiled the cord, running his hands over it again with his eyes closed. “It feels … cold to the touch. Smoother than it should be. Silk is supposed to be sleek, but … I can’t feel a trace of weave in this. It looks like it’s woven, but it isn’t.”

“Maybe … in addition to being one cord, it’s all one long fibre. Twisted together, the ends fused together seamlessly, or hidden inside where we can’t see it. Holding itself together on a molecular level. And when you break its continuity – it just disintegrates from the broken point on out. Leaving … microparticles … maybe even nanoparticles too small to detect. Brownian motion would have taken the ones from the other cord all over the room by now. I just hope there’s no physical effect from inhaling them, we’ve all … God, maybe I should write this stuff.”

“So how would you make it?”

“I haven’t the foggiest. That would definitely be a ‘sufficiently advanced technology indistinguishable from magic.’”

“Excuse me,” said Ducky, “but are you seriously proposing magic as an answer to the issues at hand here?”

“No, quite the opposite,” said John. “Merely that any advanced technology can seem like magic to those who don’t understand it. Clarke’s Third Law. The minute we do figure it out, it’s no longer magic, but science. Remember how digitalis was discovered, Ducky.”

Ducky’s frown cleared. “Ah, yes! Quite.”

“I don’t know that what I just came up with is how this stuff,” John said, taking the cord away from Sherlock and beginning to twist it into a neat skein, “actually works. Probably isn’t, but it’s something to start with, anyway. But a whole bunch of disparate ‘sufficiently advanced technologies’ can only mean one thing to me.”

“Government R&D programs? High-tech espionage?” asked Sherlock.

“I was thinking more an episode of Doctor Who, but yeah, you’re probably more on the ball. Though I’m still going to start running if I see an old blue police box on the corner of Baker Street.”

“Which way?” asked Molly, giggling.

“Towards it, naturally. I think I’d make great companion material. I could get Sherlock to give me a recommendation.”

“No, no, I’d want to go too! … What? Even I get that reference.”

“Right. So we’re going to go with something high-tech?” said John. “Maybe government, but I’m not about to ask Mycroft because he’d tell us but then he’d have to kill us. I doubt it’s something the Dursleys ever even knew about, this seems to all be circling around the nephew … probably because of the parents, maybe they left some information where somebody else knows about it? Formulas, blueprints, that sort of thing? Something the boy might have been able to claim the rights to?”

“Something that was high-end thirty-four years ago would hardly be in demand now, or worth killing for. Any patents would have expired long since.”

“Maybe blackmail material, then? Something that was only slightly damaging then, but could mean the end of a highly lucrative career, respect and privilege now?”

Sherlock tapped his lips with one finger. “Interesting speculation, but that’s all it is. We should not allow ourselves to try to fit the evidence into a narrative. Rather, we should see where the evidence itself takes us. Though you might want to keep notes for your book, John. We still have to do the analysis on the samples from the house. Molly, we’ll be up in the lab.” He picked up the box and swept out with it, leaving John to drop the skein of cord into an evidence bag, leave it for Molly, and hurry after him.

---

It was nearing eleven when they finally made it back to Baker Street, to find Mary nodding off over a stack of books and papers on Sherlock’s desk in the sitting room. “Oh thank God! Finally, an adult! I’ve spent the entire day with a six-month-old, an owl and our landlady! Do you know how exhausting she can be?”

“Who, the baby or Mrs. Hudson?” asked Sherlock while John gave Mary a peck on the cheek.

“Both – either! And the owl isn’t helping. I caught her trying to feed one of her treats to Amanda. Fortunately Amanda doesn’t seem to like chicken jerky.”

“She was just trying to help,” said Sherlock. “Weren’t you, girl?”

His pet, Gwenhwyfar, perched on top of the huge Victorian-style cage that took up the corner of the room, made a noise halfway in between a bark and a laugh.

“There, see? Be thankful it wasn’t a mouseball.”

Mary shuddered. Gwenhwyfar barked again and jumped down to Sherlock’s shoulder, cuffing him lightly with her damaged wing and grooming his dark curls with her beak. She would never fly freely, but the sitting room of 221B had been set up with her in mind, with a variety of perches and furniture that she could jump between and sit on when she felt like being out of her cage, which was entirely up to her – the door had a latch that she had learned how to operate with her beak. Sherlock had almost forgotten what furniture that wasn’t protected with carpet remnants looked like, given the damage her talons did. She was intelligent enough to keep from damaging his shoulder and his clothing, though.

“Anyway,” Mary said, yawning, “let me show you what I’ve got before I stagger up to bed. Pictures and transcripts are in the usual places in your dropboxes – I still need to edit but they should be readable. I made prints and did some research on those Rune things – sorry to tell you this, John, but they weren’t the runes from The Lord of the Rings.”

“Damn! Thought I finally had one right. Sure looked like them.”

“They’re actually Anglo-Saxon Runes, an alphabet derived from the Norse. Tolkien used them in The Hobbit, but came up with his own system of Dwarven Runes for the Rings books, so you were half right. They were used for general writing, but also for casting spells and such back in the day.”

“Were you able to translate any of the writings from the bedroom?”

“Some of them. The board, and the bedframe. Part of it’s actually modern English, just written in the Runes phonetically. Some of it looks like bastard Latin and a little Greek, and there are some bindrunes I’ll have to work on when I’m not so tired my eyes are crossing.”

“Bindrunes?” asked John.

“Those twisty bits that look like a whole bunch of runes jumbled on top of each other? That’s what you get when you take the different runes of a word or even a sentence and combine them into a design using the common elements. Some of them are traditional combinations, some were probably created by whoever did the inscribing. This one looks like a signature – it’s repeated at the beginning and end of every inscription: the letters H and P and an S hanging down beneath them. The inscription on the board is a statement that HPS controls the space and no one else can see it, repeated three times in English and in Latin. The bed is a statement that HPS sleeps well and has no bad dreams.”

“Just simple statements?”

“The idea is that by making a statement in the sacred letters that something is true, it then becomes true. Or something like that. John. Sleep.”

Sherlock frowned at the pages covered with inscriptions and Mary’s precise handwriting on the translations. “Go to bed, Mary. I’ll be downstairs running a few more tests; I can go over these while things percolate.”

Mary nodded and yawned again.

“Good night, Sherlock. Try to get at least an hour of sleep, all right?” said John, scooping the baby out of her day cot.

There was no response from Sherlock, but then John hadn’t expected one. He also didn’t expect Sherlock to actually sleep, not this early in so intriguing a case, but he felt he had to at least suggest it. With the tiny pink bundle that was his daughter cradled carefully in his arms and Mary trailing along behind, he headed up the stairs to get some sleep himself.

Sherlock moved the samples downstairs and set up a few simple tests, though as far as he was concerned, the most important one had been done at the hospital, when he tested the blood from the wall to find out which victim it came from and found it was a combination of both, used like paint in an airbrush. Final confirmation would, of course, have to wait for DNA tests, but those took time and were beyond his capacity to run himself. The murderers had left very little that could be used to identify them. Shoes custom made, not standard sizes, shaped to the feet. No identifying marks on the soles, but bespoke shoes cost a pretty penny – there are few cobblers that do that kind of work these days. No skin scrapings underneath the fingernails of the victims – there was no fight. No stray hairs or used tissues or cigarette butts or anything that a careless criminal might leave behind. No trace of a firecracker or weapons fire that might have caused the cracking sound heard by the police – no bullets, smoke burns or scorched spots, no scent of gunpowder. Not even traces of skin cells – either Petunia Dursley’s or the person who bound her – on the odd silken cords. There had been a few fingerprints found on the furniture and plenty in the upstairs room – those were being run through AFIS by the police, and hopefully there would be results in the morning, but he didn’t like having to rely on hope. The most interesting thing he had running now was the chromatograph analysis of the ink from the tip of the quill and the ink used to write the runes on the floorboard. He was willing to bet they were the same, and also that they were not standard inks, but he hadn’t got where he was by betting on things.

He used Mary’s charts and worked out the rest of the runic writings except for the bindrunes. As Mary had said, a combination of English and Latin and some words that sounded like Latin but were either bastard Latin or unbelievably obscure. But some of them … ‘alohomora’ written along the door frame just where the bolts were, running down to the doorknob. Neither Latin nor Greek. Possibly Arabic with the Al- initial syllable? And just opposite it, between the hinges – ‘colloportus’ . Not real Latin, but a combination of Latin roots. Something to do with doors, obviously. The fingerprint powder showed streaks indicating that a finger had been run across those words, top to bottom, many times. Very odd.

The most curious of all was the inscription that ran around the edge of the labyrinth, which had taken two sheets of paper which were then carefully taped together to match the lines of a full-sized copy. As Mary had noted, it both began and ended with the rune combination that the boy used as his own personal marker, HPS. Or perhaps it was HSP, since the S rune dangled off the shared element of the H and the P. Either way, it was puzzling, since Harry Potter’s middle name was James, not anything beginning with ‘S’. From there, it read “STRENGTH TO MY FRIENDS : CONFUSION TO MY ENEMIES : DESTRUCTION TO THE DARK LORD” in English. A bit of teenage hyperbole there, perhaps? And again, there was that smudge of fingerprint powder clinging to the design that showed the labyrinth had been traversed, more than a few times, with a fingertip.

Almost without thinking about it, he reached out with his own right index finger and placed it gently at the entrance of the labyrinth. Slowly, smoothly, he ran his fingertip through the first few rounds. Shortly, though, he began to feel a certain … resistance. As if he was pushing his finger through treacle, although for some reason the paper did not shift on the desktop beneath the force of it. It forced him to put more effort into the next few loops. The resistance increased the further he went, until at the last, he was sweating with the exertion of pushing it around the last circle. Then his fingertip slid into the centre point and all resistance ended. Sherlock jerked his finger away from the paper, panting and wondering why it had never occurred to him to simply lift his hand away at any point. Surely he could have done that. He looked closely at his fingertip. Nothing. No change there, though it tingled slightly and he could have sworn it would be blistered from the friction against the paper. Likewise there was no sign of disturbance on the labyrinth itself – no wrinkles, no tears, no smudges, though he was sure fingerprint powder would show he’d traced it.

With a low sigh, he pushed the sheet away from him. It was true he rarely slept during a case, but there was nothing more to do at this point and he was suddenly feeling fatigued. As John had said, surely an hour or two of sleep wouldn’t hurt. He stuffed all the runic transcriptions into a desk drawer and headed up the stairs to 221B. The huge yawn that overtook him halfway up confirmed that he’d made the right decision.