Chapter Text
John Watson woke up to the incessant ringing of the doorbell. Though he'd never admit it out loud, he understood why Sherlock had shot the damn thing.
Twice.
He got out of bed and donned his bathrobe. As he descended from his bedroom, he wondered dimly why Mrs. Hudson and Sherlock weren't annoyed enough to yell at the door. As he passed the living room, a familiar buzzing caught his attention.
His mobile was on the far desk. Odd, he remembered leaving it on his bedside table. The buzzing meant that he received a text.
He discovered half a dozen texts, all from Lestrade in the past fifteen minutes. Strange.
He checked his outgoing messages. Three were sent to Lestrade around four in the morning. John read through them in rapid succession.
Not the husband. Killer is left-handed scuba diver. Rust on flat wrench will verify.
Ringsted explosion accidental: original investigation overlooked the tailor's fingers.
Tzompantli. Emptied library likely candidate.
John was too tired, and too irritated by the continuous ringing, to remember which cases the texts could be about. He switched to messages received.
No known scuba divers connected to the case.
Arson investigation still underway.
Come immediately: 3412 New Burlington Pl.
Answer your phone
Answer your door
"Mrs. Hudson! JOHN! Someone's at the door! Can't you hear the bell?" Sherlock yelled from his room.
John went down and pulled the door open.
"Well, where is he then?" Lestrade asked immediately.
"Good morning to you, too," John replied. "Come in."
Lestrade made short work of the stairs, calling for Sherlock on his way up.
"Why on earth are you here at five in the morning?" John asked.
"Sherlock didn't say?"
"If he did, I wouldn't be asking."
"We found two bodies, decapitated. Fingerprints burned with acid. Markings carved - "
"Ah, yes, the Head Case," John replied. He added, "Working title."
"We couldn't identify the victims, and the acid was inconclusive. So was the analysis of possible weapons."
"I take it you found the heads?" John asked.
"You've no idea. But I need to get Sherlock there before the forensics team closes the place down, and we don't have much time. Donovan is holding them up at the moment."
Sherlock stepped out his room, fully dressed. From the looks of it, he had been restringing his violin.
"Well John, don't hold us up! Put some trousers on!"
Sherlock and John took a taxi and followed Lestrade's squad car to a bookshop. It hadn't been in business for years, but the building remained well kept.
John had slept for most of the trip there, but he had the vague memory of Sherlock babbling on about a weapon with chemical traces.
"Come on, John!" Sherlock said.
John followed Lestrade and Sherlock into a high-ceilinged room that reminded him of older churches, the space above feeling somehow majestic.
Except for all the heads.
Across one wall, shelves upon shelves of skulls were displayed. John could tell by looking that they were genuine skulls; the most desiccated of them sat at the top. Newer skulls, some of which still bore fragments of flesh, stretched towards the bottom. Fully-fleshed heads populated the last two shelves entirely.
"Oh, brilliant!" Sherlock said loudly. "Tzompantli. I knew it."
Lestrade pushed ahead, "Any ideas?"
"Oh, dozens."
With his magnifying glass and far too much excitement, Sherlock scanned the shelves, getting entirely too close to the heads for John's comfort.
"Now I understand the texts and the doorbell."
John considered the heads, albeit from a distance. Those with enough flesh to still have faces had a very peculiar expression: a combination of surprise, horror, and despair with a gruesome, yet unmistakable, smile. Some of them had been fixed that way after rigor with pins. He allowed his eyes to drift upwards, covering the innumerable skulls above.
"How long has this been going on?" John asked. "Some of those skulls are completely clean. Either they were skeletonized on purpose, or they've been dead for decades."
"Yeah, well, that's just it. Yesterday, we had two bodies with no heads. Now we've, what? Sixty heads and no bodies."
"You need to look into any groups with purist agendas," Sherlock said to Lestrade. "Connect such a group to anyone who could be in possession of, or a caretaker to, these grounds, and you'll have if not your murderer, then the primary accomplice."
"Purist groups?" John asked. "You think this is about race?"
"No, of course not. It's probably something about religion, or bloodlines, or family ties. Not so obvious as skin color."
"You gotta give me more than that, Sherlock," Lestrade said.
"Look at how the heads are laid out. The pattern is obvious."
"Yeah, man, woman, man, woman. 'Cept for those two, which are both women," Lestrade replied.
"Precisely. The skulls continue in a similar manner. There are about four same-sex couples, but otherwise, the pattern remains – "
John interrupted. "Sorry, couples?"
"Obviously."
"You think someone is targeting couples that are somehow 'mixed' and chopping off their heads?" Lestrade asked.
"For quite some time," Sherlock remarked. "Of course, the older heads, as John pointed out, are quite old. Likely stolen from graves. Perhaps additional victims by someone else with a similar agenda."
"That doesn't explain how you managed the couples thing," John said.
"Oh, John. Clear pattern. Obvious variation. Roughly congruent to the ten percent rule. If these people were siblings, or parents and children, there would be more variation. Those two are the newest, probably belonged to the bodies we found. Been here about three days. The next two, maybe a week, both of them. And so on. Each pair killed within the same time frame, so our killer didn't just remove heads and arrange them for the sake of sexual equality. No, they were paired together, killed together. Couples, obviously."
"Could be business partners, or people – " John began.
"The most recent acquisitions all shared scents," Sherlock added baldly.
"Please don't tell me you – " John began.
"Of course I smelled them," Sherlock interrupted. "All we have are heads. I had to collect as much data s possible. That requires the use of all the senses available."
"So you think there're, what a dozen bodies around London? All from the last week or two?" Lestrade ventured.
"Unlikely. I suspect there's either a room here that can contain them – a freezer, a basement to bury them – or access the sewers."
"You think the bodies are nearby?" Lestrade asked.
"Frankincense and limestone," Sherlock replied. "Couldn't place it when we arrived. But both can be used to cover up the scent of decay. It's not in this room, the killer using embalming fluids of some kind. So, two potent fresheners used to cover a large amount of decay, not in the room with the heads, logical conclusion: the bodies are nearby and require cover as they decompose."
"Fantastic," John said quietly. "Except for all the dead bodies."
Sherlock continued. "Whatever these symbols are beneath the heads might be illuminating. John, take photos."
"What?"
"With your phone. Photos of the iconography. It will likely be key to identifying the murderer."
"All right, Anderson's forensic techs are here, so you lot better clear out. Call me if you've got something," Lestrade said.
"We should be getting to St. Bart's," Sherlock said happily. "Let's go, John."
John finished his photo-shoot and hurried after Sherlock.
On their way to St. Bart's, John asked, "Tzompantli, that's Mesoamerican, isn't it?"
"Indeed, a skull rack. Wall of skulls."
"So, this is about religion?" John asked. "Or ritual?"
"Doubtful. The two original bodies didn't leave much to deduce. The weapon didn't leave any indication of handedness or force. The killer added a cocktail of caustic chemicals to each of the wounds, or more likely, the bladed or sharp edges of the weapon were coated with the substance, making trace evidence nearly impossible to collect."
"Nearly impossible?"
"Molly has a number of samples. I believe we can extract more data from the particles now that I've stopped the progression the chemical compound."
"Is that why you had all the windows open at midnight last night?"
"Ventilation is vital when dealing with fumes. You should probably have a physical, just in case."
"Hang on, what?"
"Relax, the flat's fine now. But I was wearing a mask. It wasn't until Mrs. Hudson complained that I recognized how potent the chemicals were."
"Is that why she was gone?" John asked.
"Yes, she went... somewhere. That's not important. This killer decapitated two people and left virtually nothing in the way of evidence, despite the physical nature of the murders. This case, John, it's brilliant!"
"Missing heads. Evidence-chewing chemical compounds. What's not to enjoy?"
Molly Hooper was just getting in when they arrived at Bart's.
"You're no good to me this way," Sherlock said quickly.
"What?" Molly asked.
"You've bags under your eyes, you've not attended to anything in the way of hygiene in the past twenty hours or so, which means you've not slept. What was it? A drink with another coworker? A late night with – "
"I was here running your tests, Sherlock!" Molly said loudly. "Sorry. Not much sleep. All the results are down in your lab."
With that, she went for some tea.
"A thank you wouldn't have killed you," John said.
"For what?"
"Molly stayed here till this morning getting these results for you."
"Ah, yes, tell her for me, will you?"
John shared tea with Molly as Sherlock riffled through reports and spoke out loud at length about acids and chemicals, though he wasn't really speaking to anyone in particular.
Molly returned to her duties – she had several autopsies lined up – after about ten minutes, leaving John to Sherlock's devices.
"Right jacket pocket, small leather book," Sherlock said after about twenty minutes.
John extracted an older book that he'd never seen before. He opened to the middle and found the pages covered in handwriting.
"What is this?" he asked. "It looks like names."
"Family trees. I need you to run the names of the recent descendants."
"Wait. Where did you get this?"
"That's unimportant."
"Unimportant? Give me one good reason I shouldn't hand this over to Lestrade!"
"Because to him and the police, this is only a book. They'll dust it for fingerprints and find nothing. They'll examine the composition of the book and find it old but otherwise unremarkable. By the time they get through all the data, at least two more people will be dead. Probably closer to four."
"Four people? What are you on about?"
"John, you took the photographs of the images underneath the heads. Check the last dog-eared pages of the book. Surely that would be the obvious thing to do."
John flipped to the marked pages and glanced through the names. The symbols carved below each head were marked in the page corners. It was like each family tree had an associated symbol. The images were too clumsy to be a family crest, but their placement suggested some kind of correlation going back generations.
"What is this?" John asked. "This one looks like a bird. That one's kind of a wolf. This one? This one's just an ugly face."
"Completely irrelevant," Sherlock said dismissively. "I've already identified the six most recent victims, all of which were on display in that room. If I'm correct, and I always assume I'm correct, then the killer has been selecting individuals out of this book. Obvious, once you connect the symbols to the pages. I figured out the names in the cab using the photos on your mobile, which allowed me to assess the next likely victims. Assuming we're not too late, we should be able to prevent the next double homicide."
"Fantastic," John said. "How are we doing that, then?"
"According to the trace evidence, the killer could be anywhere in London."
"That's not help – " John began.
But Sherlock continued as if John hadn't said anything. "But the two bodies Lestrade discovered were killed where they were found. Blood spatter made that very clear, even Anderson didn't miss it."
"Hang on, which headless bodies?"
"The two headless bodies that lead us to the wall of heads, John! Are you paying attention at all?"
"So the guy decapitated them and just left the bodies?" John asked. "But all the other recent victims, you think they were killed there. Right? So why not these two?"
"You ask the stupidest questions," Sherlock replied.
"Thanks."
"It doesn't matter why they were killed elsewhere. What does matter is the trace evidence on the victim's shoes."
"Fine, what about it?" John asked.
"Our killer is a lazy multi-tasker. He stalks and hunts multiple targets based on simple geographical convenience. That will take us straight to him."
"Us? What about Lestrade?"
"And tell him what?" Sherlock asked. "That maybe the serial killer decapitating people could be out in South Lambeth hunting his next victims?"
"Pretty much, yes."
"Hardly," Sherlock said as he put his scarf on. "Are you coming?" he added as he made his way to the door.
The cab dropped them off outside of an apartment complex in Lambeth.
"There is no way, no way you got this address from trace evidence," John said.
"We're looking for someone in casual, oddly garish clothing. Large work boots," Sherlock said. "Long coat, certainly."
"You do realize that you're describing yourself, don't you?"
"Shut up."
The streets were filled with people coming and going in the mid-afternoon sunlight. Plenty had on work boots and long coats, but John spotted none with 'garish' clothing, whatever that meant.
"So you think he's here? About in broad daylight?" John asked.
"Obviously."
"Not being caught in broad daylight."
"Looking doesn't require speaking," Sherlock said quickly.
"Garish clothing? What does that even mean?"
"Decapitation means tremendous blood spatter. Any successful serial killer would require clothing that wouldn't drench or bog down with a viscous fluid. But the killer can't wear a poncho everywhere, even in London, so his clothing will attempt to be average but by necessity must be made with waterproof fabrics. So casual but garish. Obviously."
"Sometimes you just make things up," John said.
Sherlock suddenly walked away. John waited until his black coat swished around the block's corner before following. He nearly crashed into him.
"What're you doing?"
"Small van across the street."
"Yeah, one driver," John said. "What about him?"
"He's not delivering anything. Not driving, clearly. No, he's stationary, paying for parking his vehicle where it is, but not using it. Even you must admit that's obvious."
"Couldn't he be waiting to pick something up?" John asked.
"For the past six hours?" Sherlock asked.
"Don't even tell me, I don't want to know," he replied. "So, assuming you're right – "
"Always assume that I'm right," Sherlock interrupted.
"What is it you're planning on doing, then?"
"One of us should distract him."
"Distract the man whose been decapitating people and leaving their heads on display?"
"Yes."
"You do that."
"Good, you need to open the back of his truck."
"Sorry?"
"Lestrade needs evidence, John. Evidence!" Sherlock said as he went into the general direction of the van.
John pulled out his phone. "Lestrade? Yeah, you should come now."
"John!" Sherlock barked. "What are you doing?"
"Lestrade is on his way," John said.
"What?"
"So whatever we're going to do, we've got about five minutes," John said helpfully.