Birthdays: IV. A Song of Sixpence

[willow_41z]

Title: Birthdays
IV. A Song of Sixpence
Rating: PG-13/R
Characters/Pairings: Sherlock, John, Lestrade, Donovan, Mycroft, not!Anthea, OCs
Disclaimer: I do not own any of the BBC's characters or plots.
Word Count: 6,083
Warnings: Strong off-screen violence, blood, death of OCs
A/N:
1.) Not beta'd or Britpicked
2.) PLEASE CHECK the ratings, warnings and pairings on each individual chapter, as they will be subject to change.
3.) More extensive author's notes will follow at the end of the last chapter.

December 28th
Sound penetrated the earplugs; someone was knocking on his door. John woke, looked at the clock-- 4:38, damn it-- and took out the earplugs. “What?”

Sherlock pushed open the door. “Lestrade just rang. Quadruple homicide, in Ealing. Less than an hour ago.”

John sat up and stared at him.

“You don't have to come,” Sherlock added.

“I'm awake now, aren't I?” John swung his legs out of bed. “Five minutes.”

Sherlock disappeared down the stairs. John pressed his lips together, tilted his head, and got dressed. Sherlock had handled plenty of cases on his own, and if he thought this was important enough to wake John, he was probably right. Probably. And John had no desire to return to the nightmare from which the knock had jolted him. He pulled on clothes suitable for going out, limped downstairs, and found his coat.

“Here.” Sherlock thrust a mug into his hand and tugged on his own coat. John blinked at the mug, and sniffed at it to make sure it really was the tea it appeared to be. Sherlock, on the threshold of the door, looked over his shoulder. “I haven't confused tea and glacial acetic in weeks. Come on, John!”

“Comforting,” John murmured, and followed him down the stairs.

“Any progress on the Hendon case?” he asked when they were seated in the back of a taxi.

Sherlock looked out the window. “Three possible leads.”

“What are they?”

“Suspicious withdrawals from the ex-boyfriend's bank account last week, amounts in line with hiring a shoddy assassin. Fibers on the octopus consistent with a particular brand of wool coat. Tracing the Muscadel back to the point of sale.”

“But... shoddy assassins don't buy expensive French wine, the coat's not enough to go on with, and you can't get any farther with the Muscadel until someone's awake?”

“Precisely.”

Traffic was light at that hour; the taxi deposited them behind a police car parked in front of a seedy-looking building that reminded John of his uni accommodation. The front door was unlocked, and Lestrade was standing in the doorway of the second flat on the right, silhouetted against the bright light of the crime scene floodlights. He turned when he saw them. “We're just beginning to--” Then he looked past them. “I thought you were off today, George.”

John looked over his shoulder and saw that Cyrus had followed them in.

“Sally called me anyway,” Cyrus said, and sounded faintly aggravated. “As it happens the concert was cancelled-- the soprano and tenor are both missing. Lisa was right put out.” He jerked his thumb over his shoulder. “I passed Gina on the way here, she's got the gear.”

Sherlock had pushed past Lestrade into the flat; John left Cyrus and Lestrade talking procedural matters and followed him. He stopped when he saw the scene, and closed his eyes. Oh, God.

When he opened them again, Sherlock was bending over one of the bodies. There were four of them, all girls: two on the sofa in knickers and shirts, one slumped against the wall in a dressing gown, one on the floor in a tracksuit. They all had stab wounds to the chest or torso, and there was a large knife still in the stomach of the girl on the end of the sofa. One of them had a joint in her hand, and another joint was partially crushed on the floor.

“Is this... connected?” John said. “Someone going after students, girls?”

Sherlock was examining the girl in the tracksuit. “Completely different mode of operation. The

killer came to them. Same build, though, as the one who killed Annie Pratt. Different handedness, however...” He moved on to the girls on the sofa.

Cyrus and Minnelli came in and started to process the scene. Sherlock was still looking at the bodies. It was unusual, John realized, for Lestrade to call Sherlock in before the rest of his team even got there-- very unusual. The detective inspector was more concerned about this than he was letting on.

Lestrade came in. “Press is going to have a bloody field day with this one,” he muttered. “Sherlock, what've you got?”

Sherlock straightened. “Four students, flatmates, all habitual marijuana users. The one on the floor also used heroin on a semi-regular basis. They'd ordered takeaway-- Thai, judging by the table-- and opened the door for the delivery man, which is how the killer got inside the building. After the man left, he knocked. He stabbed the girl who opened the door, shoved her down, made a shallow cut across the torso of the girl in the red shirt, stepped around her, stabbed the girl in the dressing gown while she was still sitting down, crossed the room, pulled the girl in the blue shirt away from the window where she was trying to escape, made the deep cut you see in her abdomen, and left the blade in the abdomen of the girl in the red shirt, who had recovered enough to attempt to grapple with him. The girl in the dressing gown was trying to dial 999 on her mobile phone; he took it from her and left by the window. It took at most forty-five seconds. You'll find the mobile in the first skip outside, and questioning the next-door neighbor who heard the screams and rang emergency will tell you that he is a man of slight stature and average height and was wearing a mask. None of the girls managed to leave a mark on him, and...” he trailed off, staring at the window sill.

“Sherlock?” John prompted, following his gaze.

Sherlock took out his hand lens and squatted on his heels. “... and we're looking for an ambidextrous serial killer with an interest in cephalopods,” he finished.

“Hang on. You're saying this is connected to Annie Pratt?”

“Coat fibers.” Sherlock picked something up with tweezers and put it in an evidence bag.

“Well, maybe the killers just... had the same style of coat.” Lestrade shoved his hands in his pocket and frowned.

“And the same shoe size, height, and weight? Use your eyes for something besides glaring at me, Lestrade.” Sherlock stood, lifted the sash of the window, put his head out, and then climbed into the alley. John sighed, and went round by the door at the end of the hallway outside.

He'd expected to find Sherlock halfway to Brent already, but he was kneeling by a skip next to the window. John came up behind him and tried to deduce was what of interest about the jumbled pile of boxes. “His foot caught here,” Sherlock said, indicating a particular box. “It was the third box in the stack. This way!” He straightened up and took off, John following closely behind.

“Where are we going?” John asked. “Isn't he long gone by now?”

“Direction he was going when he tripped over the box indicates he took the first left out of the alley,” Sherlock said. “But if he'd kept going that would have brought him out right in front of that pub at closing time. Clearly he didn't know the area. He's got splashes of blood across the front of his coat and left shin, too conspicuous until he could change clothes, so--” He skidded around the corner into an even narrower alley, this one damp and mossy. “He would have turned here.”

“Hang on. Sherlock, are you trying to catch this bloke? Because I didn't bring...”

“He's long gone by now,” Sherlock said, crouching over a patch of moss.

“Then why--” But Sherlock had straightened up and was running down the alley.

It didn't take John long to figure out that Sherlock was looking for something, but that was as far as he got; he couldn't figure out the connection between trampled patches of moss, a discarded doll, and an empty package of crisps. Sherlock didn't explain, and John gave up asking. It felt like they'd run across half of London, and the sky was beginning to lighten in the east, when they turned a corner and he saw a line of police cars... they'd come back to the crime scene.

Sherlock paused outside the building, then barged through the front door to where Lestrade was talking with Donovan and Cyrus. “Killer is a man, between fifty and sixty, beginning to have arthritis in his right knee or ankle. Came on foot from the east, turned east at every opportunity when leaving. The knife is his own, he's owned it for some time, but it's an unusual design, probably purchased from a Japanese sushi restaurant going out of business. Given the corrosion pattern on the handle, he lives in Lambeth. He traveled to both Hendon and here on foot, which means these weren't random killings, he had a reason for coming here.”

Lestrade, Donovan and Cyrus were all staring at Sherlock. Lestrade recovered first. “Why is he going after female students? None of them showed signs of rape or sexual assault... If they're not random killings, then what links these five women?”

“I don't know. Why don't you find out?”

John followed him to the street. “Where now?”

“Our killer has expensive tastes: Muscadel from France, and now a Loden wool coat. Relatively new, by the looks of the fibers.” He took a small bag from the inside pocket of his coat and scrutinized it carefully as the taxi pulled up to the curb. “I'd say this season or last.” His phone rang. “Sherlock Holmes.” By the rapid-fire French that followed, John concluded that it was about the Muscadel.

“A lead?” he asked when Sherlock hung up.

“Possibly. Stop!” He ducked out of the cab, handed something to the person wrapped in ragged garments and huddled in the doorway of the abandoned building to their right, and came back to the cab.

They went back to Baker Street. Sherlock scrutinized the wool samples under the microscope, muttering about lanolin composition. John fixed breakfast and took a catnap on the sofa until a ringing mobile woke him. “Sherlock,” he said groggily, before waking up enough to realize that it was his mobile. “Hello?”

“John, I'm glad I caught you.” It was his boss. “Listen... any chance you could work a double tomorrow?”

John hesitated, glanced into the kitchen, and licked his lips. “Er...”

“Thompson's been involved in a hit-and-run across the city, and McGerry's caught the flu from a patient and had to be admitted for dehydration. Raner said she can cover for Thompson, but I need you to cover for McGerry until we can get someone from another hospital.” Pause. “I'll have someone cover for you later in the week, you can have some more time off.”

John suppressed a sigh. “Yes, all right.”

“Thanks, John.”

“I can't run round with you tomorrow, I've got to work,” John said, coming into the kitchen to put the kettle on.

“Dull.”

“Tea?”

“Yes.”

John filled it from the tap. “You think he's going to strike again?”

“Why shouldn't he? The only question is, when.”

“What can I--”

“The door.”

John blinked. Yes, that was a knock. He ran downstairs and opened the door. A tall woman bundled up to her eyes with a ragged coat and scarf handed him a piece of paper and turned away. “Er, thanks?” he called after her.

It was a list of streets. “What's this?” he asked, handing it to Sherlock.

“The route the killer took, as far as Battersea Park. Pass me my phone, it's in my coat.”

John returned with the phone. “That was fast.”

“A lot easier than finding the Golem.” He looked up from the microscope and sent a text.

John leaned over the sink and frowned. The images were running together in his head: the kid who had died on his last shift, and the blood spattered around the bodies of the four girls. He needed sleep...

“Ah!” The kettle whistled as Sherlock sprang up from the stool.

“Do you want me to come with you?” John called into the living room.

“No, stay here in case anyone else comes by. I shouldn't be long.”

John took another nap on the sofa, waking when Sherlock returned an hour later. “Mmm,” he said, trying to stretch out his shoulder after falling asleep in an uncomfortable position. “You found something.”

“The names of everyone who purchased the killer's coat-- firsthand-- in the London area in the last two years, yes.” He waved a sheaf of papers.

John sat up. “What?”

“It's a unique coat. And a long list.” Sherlock's phone beeped. He grabbed it. “Excellent! Oh, clever girl.”

“What?”

“The girl who was trying to dial 999, she snapped a photo of the killer before he got the phone away from her.”

John stood up and came into the kitchen to look over Sherlock's shoulder. The image was blurry and dark, and the man's mouth was covered by a mask, but his face was still halfway visible. He looked... bland. Nothing particularly remarkable about him at all. Mousy brown hair, straight nose, regular features. 

Sherlock picked up his laptop from the table. “Sending it and the list to passport control,” Sherlock murmured. “They should be able to cross-reference and tell us who the killer is. Then it's only a matter of finding him.” His phone beeped again; he glanced at it, and his eyebrows furrowed. He muttered something that sounded like “Mycroft.”

“What about him?”

“I gave him the route and the time and asked for the CCTV images. I even told him it was a serial killer. He 'regrets that he will be unable to help me.'”

John frowned. “That doesn't seem like him.”

“You don't know Mycroft. It doesn't matter now, we have the picture.”

John glanced at the time: half eleven. Sherlock got up and began to pace. “The connection. What's the connection between the five?”

“All students?”

“Yes. Obviously.”

“Annie... Annie Pratt was reading chemistry, you said. And the other four, were doing pot. Drugs?”

Sherlock ran both hands through his hair. “Meth is usually the product of choice to be synthesized.”

“Maybe... someone they all knew? Or someone two of them knew, and the killer had to kill all of them to cover his tracks.”

“There are easier ways to eliminate someone besides stabbing them and their three closest friends.”

“Could have been a warning... or it was urgent.”

“No drug paraphernalia anywhere in that sitting room. Unlikely they were into anything stronger.” He opened his laptop and began to pull up information about the four dead girls. John didn't ask how he knew their names.

For the next hour, Sherlock alternated between pacing and using his computer. Then he slapped on two nicotine patches and stretched out on the sofa. “Shut up, I need to think.”

John continued to be silent. Sherlock's eyes closed, and his breathing slowed and deepened; John could have sworn he was asleep, except that he knew Sherlock's brain would never let him sleep in the middle of a case like this. He reached for his laptop, just within arm's length on the coffee table--

“I said, I need to think.”

John tilted his head, leaned back, and stared at the ceiling. For a long time.

Someone knocked on the door. “Oh, what now?” Sherlock demanded. “John--”

“I'm going.”

“Don't let anyone in.”

It wasn't one of the homeless network. “I need to talk to Sherlock,” Lestrade said, and stepped inside before John could even think of closing the door.

From upstairs came a noise of disgust; Lestrade and John exchanged glances, John shrugged, Lestrade shook his head.

“What is it, I was trying to think,” Sherlock said, still staring at the ceiling.

“Passport control contacted me,” Lestrade said.

Sherlock sat upright. “Why didn't they contact me?”

“You turned your phone off when you were thinking,” John said.

“Oh.” Sherlock reached for his coat. “Name?”

“There isn't one,” Lestrade said.

Sherlock stared at him. “What?”

“No one on your list has gone to France in the last six months, and neither has anyone matching the picture of the killer.”

Sherlock straightened. “It was a gift.”

“I brought you these.” Lestrade took a sheaf of papers out of his coat. “Background checks on two of the dead girls-- they'd recently applied for jobs, and they'd both had run-ins with the law. Possession. Details pending on the other two.”

Sherlock took the papers and looked through them rapidly. “None of this is relevant.” He tossed it down. “The wine. It's the key to all this, and I don't know why.”

“The wine? What about the hen?”

John and Sherlock stared at him.

Lestrade looked faintly embarrassed. “'s what we called the female octopi, where I grew up. Hens. My sister worked for extra money at a fishmonger's-- well. I'm going back to the Yard: between these two and the Christmas Day strangling at Le Poirier, the press is having a field day. Look, Sherlock, text me the minute you come up with anything, all right?”

Sherlock was still staring at him. “What strangling?”

“I told you about it,” John said. “You said the name was ridiculous.”

“You never mentioned the name of the pub.” There was a new sharpness to his voice, and he was typing rapidly on his mobile.

Lestrade glanced at John, who shook his head, as bewildered as the other man. “Sherlock? What is it?” Lestrade asked.

Silence. “We're missing two bodies,” Sherlock said finally.

“What?”

“Obvious, in retrospect. Obvious.” He ran his fingers through his hair. “The note. Annie Pratt wasn't drunk and she didn't write the note, so the language matters. Two unusual phrases: I breathe lonely air; I'll be free, I won't return home. Both,” he held up the screen, “found in songs by the same band, both written by an artist nicknamed 'Hen.' And then there's the station--”

“Christ,” John said. “Hendon. The station code. You think--?”

“Two days earlier, a woman found strangled in Le Poirier, the pear tree, on Christmas day.”

“Hang on,” Lestrade said. “Are you saying this has to do with the twelve days of Christmas?” He looked incredulous. “You can't honestly think that--”

“I do think, and it's more than you do!” Sherlock snapped. “She had an octopus in her throat, Lestrade, improbable events require improbable explanations. None of the people who knew Annie Pratt would be where she was had reason to want her dead, therefore, her identity was irrelevant. Who waits around a train station after hours with a cephalopod, a fake suicide note and a bottle of expensive French wine except someone with a point to make?”

“So the girls, the four girls--”

“Four females smoking marijuana. Four,” Sherlock grimaced. “Collie birds. Good God, what are the criminal classes coming to, he deserves to be hanged for the pun alone.”

“Sherlock--”

“Re-check the Christmas Day murder, and I guarantee you'll find a connection with a partridge,” Sherlock cut him off.

“What about the... the two turtledoves?” John asked.

“And check every morgue for any intakes in the past forty-eight hours with strangulation or stab wounds. There should be a pair of them.”

Lestrade still looked flummoxed. “Suppose it's more to go on than we've got,” he murmured.

Sherlock was reaching for his coat. “John, fetch the wine, it's in the cabinet. And tell Mrs Hudson to listen for the door while we're gone.”

“Where are you going?” Lestrade demanded.

“Familial obligations,” Sherlock said. “'Tis the season. Send me the details of the Christmas murder!”

Lestrade looked appalled, presumably at the prospect of Sherlock's family. John felt appalled, but that was because he'd actually met the man.

“You're asking Mycroft's help?” he asked when they were in the back of the taxi.

“No, I'm consulting my cousin about representations of Muscadel in baroque painting. Of course I'm asking Mycroft's help.” His mouth tightened momentarily. “There are too many pieces. They're not fitting together, and I need information only he can give me.”

They stopped, some time later, in front of the nondescript office building that John remembered from April. Sherlock ran up the front stairs; John caught up with him in front of the massive desk in time to hear him arguing with the secretary. “What do you mean, you can't let me in?” Sherlock demanded.

“Mr Holmes has gone Out.” The man smiled imperturbably. “Would you like to leave a message for your brother?”

“I just texted him--”

“Hello.” They both turned. Mycroft's PA, she of the mysterious name-- though, John thought, Sherlock probably knew it-- and Blackberry attachment, was standing behind them, texting, of course. She glanced up. “Come with me.”

There was a car waiting outside. Sherlock climbed into the front, leaving John in the back with... whatever her name was. “Hello,” he said.

After a moment, she looked up. “Hello.”

“So... how've you been?”

The smile that he was pretty sure was fake. “Fine.”

From the front seat, Sherlock said something that might have been “Oh, God.” The driver's profile changed, just a little. John repressed a sigh, and stared out the window.

They stopped. John got out and let Mycroft's PA slide out before shutting the door. Anthea, or not, unlocked the door, letting them into a small antechamber, and then entered a code on a sheltered, electronic touchpad. Something buzzed, and the second door swung open. John looked at it as they passed: two inches of metal, with wood on either side.

They followed her up the stairs to a sitting room that was everything 221b wasn't: impeccably neat and flawlessly decorated. Mycroft was seated in front of a small desk, frowning at a laptop that looked out of place in the wood and leather of the room. As soon as Sherlock and John appeared, he shut it and smiled at them. “Ah. Yes. Thank you,” he said to... his PA. “Have a seat, won't you?”

John sat. Sherlock paced, coat flaring around him.

“Your request about the CCTV footage--” Mycroft began.

“It's not about that.” Then Sherlock stopped and looked at his brother. “What about it?”

“Oh, I was just going to offer my, ah... further apologies.”

Sherlock's eyebrows furrowed. There was thirty seconds of silence. Then: “You're having problems at your job.”

Mycroft stopped smiling. “We have a mole.”

John knew he didn't understand half of what Mycroft did, and was quite content to leave matters that way, but he knew enough to make that statement a frightening one. If Mycroft couldn't catch the spy...

“This individual,” Mycroft continued, adjusting something on his desk, “has been interfering with the cameras. Unfortunately, the footage you requested was one of the casualties.”

“I trust you'll deal with it with your usual acumen.” Sherlock already sounded bored.

“Indeed.” Mycroft smiled again. “You're here about a case.”

“Yes.” Sherlock resumed pacing. “I... need your help.” John wondered how much effort it had taken him to make that admission.

Mycroft was magnanimous in victory, if that was what it was. “In what respect?”

“It's a serial killer.” Sherlock threw himself into a chair, looking incongruous with the orderly respectability of the furniture. “One woman was strangled on Christmas Day in Le Poirier. One woman was strangled at Hendon yesterday, and left to die with an octopus in her throat. The killer left a bottle of Muscadel beside her. Four girls were stabbed today in Ealing as they shared joints at their flat. All were killed early in the morning. The killer is a slender man, slightly arthritic, ambidextrous: he used predominantly his left hand to strangle Annie Pratt and his right hand to commit today's murders. He lives in Lambeth. The Muscadel came from France within the last six months but either that or his coat was a gift, because the photo, billing lists, and passport control's information are incongruous. So.” He put his hands together in front of his chin and stared at his brother. “Feeling public-spirited?”

“Annie Pratt was killed at Hendon?” Mycroft asked after a moment.

“Is it still one sugar, John?”

John looked up, distracted from the conversation, to find Anthea-or-not at his elbow, smiling sweetly and holding two mugs of tea. “Er, yes, how did you... never mind. Thank you.”

“You're welcome.” She took the other mug to Sherlock and set it on the table at his elbow, then disappeared back to what looked like the kitchen.

“Mmm,” Mycroft said, opening his laptop and frowning. “Yes. Sherlock, I see you're still not eating on cases.”

“It slows me down.”

“Yes, hypoglycemia is always so invigorating.”

“As if you'd know.”

Mycroft began to type. “I confess, John, I'd hoped you might be able to persuade him otherwise.”

“Then you don't know either me or your brother very well,” John said.

Sherlock smiled. Mycroft stopped typing to stare at John over the top of the laptop for a moment. Then he resumed whatever he was doing, and somewhere, a printer began to click and whirr.

“Annie Pratt was chosen at random, she... happened to be in Hendon at the right time,” Mycroft said, sounding contemplative. “So was Holly Whitehead-- not a student, by the way. But the other four, he invaded their home.” He got up, walked to the other side of the room, and opened a cabinet. “Both actions make sense if the lyrics are the most important part of his mode of operation.” He took a thin stack of paper from the printer and handed it to Sherlock. “He... must have a strange fixation with them, though the murders thus far have shown a willingness to be quite flexible in their interpretation. What must be important to him is that there is some connection between the killings and the lyrics of the song.”

Sherlock leafed through the pages, and then looked up sharply. “Names.”

“Deaths. From the last ten years,” Mycroft said. “All heterosexual couples who died violently within thirteen days of each other, from Christmas Eve to January 6^th. In each case, at least one person was either stabbed or strangled, but I think you'll find the last category, with one of each, most informative. Children are listed where available.” He nodded at Sherlock. “If you need earlier than that, do let me know.” He returned to the laptop. “I've taken the liberty of also sending the file to that detective inspector you prefer to collaborate with at Scotland Yard. I see he's in charge of the investigations.”

“Hmm,” Sherlock said.

Mycroft smiled thinly. “You're welcome, Sherlock.”

Sherlock stood, leaving his tea untouched. At the door, he stopped and leaned back into the room. “The homeless network is really invaluable,” he said.

Mycroft raised one eyebrow. “I will keep that in mind,” he replied, and John realized that that was the closest to 'thank you' that Sherlock was going to come.

Sherlock disappeared out the door. John swallowed the rest of his tea and grabbed his coat.

“Goodbye, John. Do try to be careful. For the both of you.”

“Yes,” John said, and “thank you,” because Sherlock hadn't said it.

The car was waiting at the bottom of the steps for them, sans Anthea-or-not, and Sherlock glared at it, but got in. “Baker Street,” he said. “22-”

“Yes, Mr Holmes, I know,” the driver said, and they pulled away from the curb.

Sherlock was leafing through the pages rapidly, eyes moving quickly as if he was scanning the entire thing and putting it in his hard drive. He probably was. “Here,” he said, and handed John the sheaf as he took out his phone. “There.” He pointed, and made a call. “It's me. The killer's name is Jared Wilkins.” Pause. “Yes.” He hung up. “Lestrade's meeting us at the flat. By the time we get there they'll know where he lives.”

John looked around the back of the car. “Hang on, where did the... did you leave it in the taxi?”

“It's in Mycroft's kitchen.”

“Oh.” John hadn't even seen Sherlock pick up the bag, let alone go into the kitchen, but never mind. “Jared Wilkins.”

Sherlock was typing quickly on his phone. “Civil servant,” he said. “His elderly mother stabbed on Christmas two years ago by a robber. His father was hospitalized for shock and strangled by one of the nurses on Epiphany.” He scanned the screen quickly. “They won't find him at his flat.”

The car let them out. Sherlock went up the stairs, two at a time; John continued on to the second floor and his bedroom. His gun was in the drawer, in the holster that had been Sherlock's Christmas present to him, along with a pair of gloves; he fastened it at the small of his back, put his coat back on, and ran back downstairs.

“There's an ARV on its way,” Lestrade said.

“Unnecessary. You won't find him there.”

“Then why are you coming?”

“To tell you where he's gone. Have you found the partridge connection yet?”

Lestrade looked tired. “I had Donovan recheck. It wasn't ivy, it was something called partridge vine.”

Sherlock smiled, the smile that didn't reach his eyes. “And it only took you four days, well done.”

Sherlock hailed a taxi and they followed Lestrade's car to Wilkins's flat, which was in Lambeth. Lestrade made Sherlock and John stand out of the way as the armed officers forced the door and searched the flat.

“Nobody here,” the commanding officer reported. “Want to let your team in?”

“Right,” Lestrade said. Donovan rolled her eyes as Sherlock brushed past the man into the flat; the SFO looked askance at him. “Consultant,” Lestrade explained. “This sort of thing is his specialty.”

John went inside and found Sherlock in the spare, nearly meager bedroom: one bed, a table, one chair, and a chest of drawers. It was familiar enough that John wondered if this Wilkins bloke was ex-military. Sherlock opened and shut the drawers rapidly, looked out the window, and went into the attached W. C. as Lestrade's team began to come in.

Sherlock went into the kitchen and began a rapid survey of the drawers, staring intently when he found the knife drawer. “Tomorrow will be a strangling,” he said.

“Why?” Lestrade asked.

“He hasn't been here since Christmas Eve-- the plant is wilting, and there is rain in the rain gauge from Christmas Eve but not Christmas Day. Therefore he must have taken everything with him, as evidenced by the gaps in his drawers. He is missing several changes of clothes, nearly all the trousers he has, so he's anticipating ruining them. There is a space in the drawer organizer here that is completely empty, and it fits the murder weapon from this morning. Judging by the height, he had a set of six. Six knives: he strangled on the first and third days but stabbed on the fourth. Therefore, he plans to alternate stabbing and strangling.”

“So where is he?” Lestrade asked after a moment.

“Hard to tell,” Sherlock murmured. “He may have booked a different hotel room for each night. He anticipated his flat would be compromised, so, it would be under an assumed name. There is a false bottom in his bedside table drawer, and it's empty; presumably it held things like fake passports and identification cards.” He went back into the bedroom.

John went over to the one bookshelf in the sitting room. It was nearly empty, with a single row of similarly-bound novels with cheap covers, and a half row of nonfiction above that. There was an empty spot between an atlas and the London A to Z. “These were his mother's books,” Sherlock said behind him, and took one off the shelf. “He's taken the map of London.” He frowned, and pulled the atlas off the shelf. “Turn the light on.”

John flicked on the light.

“Islington,” Sherlock said.

“Sorry?”

“There's a plastic sleeve in the rubbish bin from where he bought a new map, because this one got wet and ran. It left an imprint when he put it back on the shelf, and the imprint is of Islington.”

“You think it means--”

“Methodical man leaves a map folded up wrong, of course it means something. The last murder he planned is going to be in Islington. It didn't rain hard for ten days before Christmas Eve. But which one did he plan last?” He tapped the back of the atlas. “He only killed one person yesterday.”

“So...?”

“It's as Mycroft said: he doesn't care about precision.”

“Sherlock, you said you could tell me where this man is,” Lestrade said.

“I need more data. I need to take his shoes to Bart's.”

Lestrade hesitated. “Clear them with George first,” he said finally.

Sherlock's preferred lab was empty, and he commandeered it, removing soil from the soles and examining it under the microscope. “Definitely Islington,” he said after several moments. “The north side. Also...” Pause. “Willesden. He's favoring the northwest and staying clear of south of the river, why?”

“You said you thought he was holing up there.”

“Hmm.” Sherlock scrutinized the samples silently. “Brent, and back to Islington.”

“He visited each of these places in advance, then?”

“Yes. How would he have known where to find the four girls smoking unless he had previously observed their habits?” Sherlock took out his mobile and sent a text, then switched off the microscope and stared at the far wall. “Five golden rings. What does that mean to you, John?”

“A jeweler is the first thing that comes to mind, of course. Or boxers... something with a clock, he's going to kill someone at five in the morning? They have all been in the morning.”

“Originally the lyrics referred to ring-necked pheasants. Like the four colley birds, it became corrupted.” He leaned back in the chair and stared at the ceiling. “Too many options. He's not doing this logically.”

It was after dark by the time they went back to Baker Street. Sherlock paced, played Beethoven frantically, and applied fresh nicotine patches. John made tea, checked his email, and kept an eye on Sherlock to make sure the number of patches stayed under control. Eventually, after having been sitting down for a while, he became aware of a deep weariness, and remembered that he had to work a double the next day. It was always unprofessional to fall asleep on the job.

Sherlock went out and returned with a list of places where Jared Wilkins had been spotted in the past two weeks. He cross-referenced this with the results of the soil sample analysis. “Tomorrow will be Brent,” he said finally. “But where?” He ran his hands through his hair.

“I'm going to call it a night,” John said. “Sherlock...”

His flatmate looked up at him.

“Oh, never mind.” Saying be careful would just provoke the “you're-an-idiot” look. “Happy hunting tomorrow.”

Author's notes:

The band Sherlock is referring to is Haken, and the album is Aquarius. "Collie" is rather obscure slang for marijuana.

In ACD!canon, Sherlock sometimes takes problems to Mycroft, and I wanted to explore that here.