Charlie obliging started to whimper as soon as she understood that she was being put into her much-hated car seat. By the time John parked outside the Slade Street practice twenty-five minutes later she was bawling, tears cascading down her chubby cheeks in a way that racked her father with guilt.

"I'll make it up to you, Charlie, promise," he muttered as he freed her from the car seat. It had started to drizzle again, which wasn't helping things. He shut the car door with his knee, fumbling for the keyless lock. "Won't be long here..."

The waiting room wasn't as crowded as John had expected it to be, containing only a handful of people. A handful of people, nonetheless, who probably had set appointments and real illnesses. Behind the counter sat a flustered-looking secretary, with purple-painted nails and fluffy brown hair escaping from where she'd pinned it severely behind her ears.

"Hi," he said to her over Charlie's wails, affecting to look as frazzled and incompetent as possible. "My name's John Watson… I've never been here before, I mean, I haven't got an appointment or anything, but I was wondering – "

She shook her head. "Sorry," she said, though she really didn't sound sorry at all. "Dr. Harper can only be seen by appointment. There's a clinic on the Claverton Road that takes walk-ins…"

"Please," John said, hoisting Charlie on one hip and almost proud of her when she continued to wail on cue. "Look, I've just gone to change her nappy and she's all over nappy-rash. She's bleeding. I can't even put her in the bath. My wife's going to kill me."

He waited. Now he had only to find out whether Dr. Harper, or his secretary at least, was the sort of person who would publicly turn away an apparently helpless father and a baby screaming in pain. It had been a long time since John had worked in general practice, but he remembered distinctly the unofficial rule most offices had – babies went into the express lane.

The woman stood up, just as the phone in front of her began to ring. Exasperated, she picked it up, listening for a second.

"Okay," she said into the receiver. "I have a walk-in here, a John Watson with a baby suffering severe nappy rash… how old did you say she was?" she asked John, cupping the receiver for a moment.

"Thirteen months."

"Thirteen months," she relayed, then listened for a few more seconds. "Yes. Right away…" She hung up the line and looked over the counter at John. "You can go in," she said wearily.

As he went, John cast her a sympathetic look. After all, she was the one who now had to field a room full of pissed off patients who had been moved back in the queue.

Dr. Harper was, roughly, everything that Vanessa Thompson had claimed he was – greying, early forties, square-rimmed glasses. John silently conceded that he couldn't have expected a more exact description of such a completely unmemorable person.

"Oh, dear," Harper said sympathetically as John brought Charlie in. "Who's this unhappy little girl, then?"

"Charlie," John managed to get in over the noise. "Charlotte."

"Nappy rash is no fun, is it, Charlie?" Dr. Harper gestured to the high, deep-padded examination table. "Come on, let's have a look at you, then…"

John steeled himself, but he continued in his role as hapless parent until Harper had taken Charlie's nappy off to view the extent of the damage.

He looked over sharply at John, eyes full of accusation. "Nappy rash, you said?"

"Yeah, I lied about that," John said unrepentantly, struggling to keep Charlie still enough to dress her again. "Sorry. You've probably not heard of me, but you might have heard of my colleague, Sherlock Holmes. We're currently investigating a murder. You were called out by the Met to attend the crime scene last night."

"Yes," Harper said warily.

"A woman found the body of her soon-to-be-ex-husband in his kitchen," John went on, pulling a milk biscuit out of Charlie's pink My Little Pony backpack and trying to distract her with it. "She'd had a nasty shock, all right. You prescribed Zopiclone for her. She's now in hospital."

Harper raised his eyebrows and, for a second, looked alarmed. "I prescribed it to her well within guidelines…"

"Well, yes," John conceded. "Very likely you did. What I'm wondering about is that you prescribed it at all. Now look, you're not the only doctor in the room. You and I about the same age, and we probably both read medicine and took prac in the United Kingdom. I've never prescribed Zopiclone in my life, and I was dealing almost wholly with the armed forces at one point. You don't get prescription-happy on drugs like that."

Dr. Harper pursed his lips defensively. "All right," he said. "What exactly would you have given her?"

"Me? A sugar pill, and maybe a box of tissues."

Over his years of working with Sherlock, John had given lots of distressed clients, from Lucy Harrison to Henry Knight, "something to help you sleep". In nine out of ten cases it had been a sugar pill, though once or twice he'd been caught out and had to settle for paracetamol. Not one client had ever commented on the unusual flavour of the medication he handed out, and in most cases, they'd even claimed to have had a great night's sleep after.

"A woman who's just found the battered corpse of the man she had two kids with is going to get a rotten night's sleep, no matter what," he went on, running his fingers over Charlie's hair as she hiccupped over her biscuit. "She doesn't need sedatives. She needs someone to call a relative or friend and get her and the kids a safe place to sleep for the night. Anyway," he continued, realising this line of discussion wasn't making a friend of Roland Harper. "Have you ever prescribed Zopiclone for any patient by the name of Biondi?"

"You know I can't answer that," Harper returned, setting his mouth in a hard line. "I'm surprised you had the nerve to ask me something like that."

"So am I, really, but right now I'm desperate enough to give it a try. The killer's still at large, you know. He's killed two people already, and we think he'll try again."

"He?"

John blinked. "Are you telling me you've prescribed Zopiclone to a woman with the surname of Biondi?"

"I'm not telling you anything. What good would that do you, anyhow? There are hundreds of GPs in London, who've written out who-knows-how-many prescriptions for Zopiclone in the past few weeks."

"True," John conceded. It was on the tip of his tongue to say but none of those GPs are associated with Scotland Yard, but he wisely decided to keep that point close to his chest. Harper stood up and reached out for the door to show his patient out.

"If you go now, we'll say no more about this, Dr. Watson," he said. "I don't enjoy being lied to."

"Yeah, well, I don't enjoy watching friends suffer because of a murderous criminal." John stood up, resigned, and hauled Charlie up from the examination table. "You can understand that I had to give it a try."

"I do. It didn't work. Make an appointment next time, if your daughter actually is sick." Harper went back to his desk and reached out to pick up the phone. Just as John was about to shut the door behind himself, he heard Harper call him softly. He paused, one hand resting on the doorknob.

"There's one thing, before you go," Harper said. "You know I can't tell you if someone's my patient. But I think I can tell you if someone isn't. If it helps your investigation, I've never had a patient by the name of Biondi."

"What about…" John searched around in his memory for the surname of the kids Sherlock had interviewed, along with Donovan and the other female officer he knew as the blonde one. "What about by the name of 'Trent'?"

Harper's eyes narrowed. "No patients by that name, either," he said. "No more questions."

Well, John reflected to himself as he struggled to clip Charlie back into her car seat. Process of elimination, but it was a start. The drugs given to Celeste hadn't come from Vanessa Thompson, the Trent kids or anyone in Celeste's immediate family.

Only a few million suspects to sift through, now. He was distracted from his thoughts when his phone rang, resulting in a mad hunt through his pockets before he located it. "Yeah?" he said, hoping to God it was Sherlock.

"John."

Anderson again.

"Hi." John kneaded his forehead with the tips of two fingers. "How can I help?"

"There's something I think you should see… I can't get hold of Sherlock, and I can't explain it to over the phone. Could you come to headquarters?"

John glanced at his watch. "Yeah," he said, "if you can give me half an hour."

"Text me when you're here and I'll let you in."

~~o0o~~

Melissa had coasted the car to a halt directly in the no-stopping zone outside of New Scotland Yard. Lestrade, jacket glistening with rain, didn't bother to point it out to her as he got in and slammed the door after himself. He took off the jacket and tossed it into the back seat. No Hayley.

"So…?" he demanded.

"So Pamela is off the wedding list," she seethed, flicking on the indicator with as much vim as if she were slapping her future sister-in-law across the face.

He stared at her. "What? What happened?"

"I'm afraid we had words."

"Oh, my God –"

"No, Greg. I know you like to keep the peace, but she had no right to say what she did. I'll summarise and tell you it was neither pleasant nor fair to you." She paused, checking her shoulder for oncoming traffic as she merged lanes. "Actually, I'm not so sure your mother and I are on speaking terms anymore, either."

He heaved a sigh. Well, that was nothing new. Most of the time he wasn't on speaking terms with his opinionated, sharp-tongued mother. A favourite with Julie, she had never approved of the divorce, let alone his new relationship and engagement. She had a habit of referring to Melissa as "Melinda", "Melanie" or, when she was really displeased, "that girl" and "her".

"So Pam hasn't heard from Matthew?" he tried again.

She reached out and rubbed his shoulder. "Darling," she said gently. "Don't you think that that would have been the first thing I'd told you, if she had? No sign of him. I'm so sorry. You've not heard from Sherlock...?"

"No." He blinked twice in rapid succession and glanced at the back seat again. "Where's Hayley?"

"At the museum – she thinks Matthew might be holed up there in the reading room. I'd have never thought of that. I dropped her off at the station."

"Wait, you dropped her off at the station?" he demanded, voice pitched high with sudden anxiety. "On her own?"

Melissa blinked. "Yes," she said.

"Jesus Christ, Mel! Are you out of your bloody mind? There is a serial killer running around the place targeting my family and my team, and you left her to look for her brother on her own?"

"I know you're upset," she said through gritted teeth, clutching the steering wheel with white knuckles. "So I am choosing to give you exactly one free pass on your tone of voice. Greg, she's eighteen. Old enough to be responsible for herself-"

"She isn't responsible enough to avoid being murdered!"

"You really think someone's going to target Hayley? Or are you just being paranoid because you love her?"

Lestrade swallowed heavily. "I don't know," he said, taking a deep, slightly shaky breath. His fingers tweaked the crook of his elbow where, under his jacket, he had a sticking plaster over the needle mark Anderson's blood test had left in its wake. "Celeste could have been… well, it could have been anyone who killed Celeste. But Thompson… I'm the one who knew both victims. Not Matthew. I don't think he could have picked Thompson out of a photograph. What if this is someone after me? My kids? You?"

Melissa was silent for a few seconds. "Funny you should say that," she said. "It crossed my mind that it could be related to one of my clients, even though I didn't really know either of the victims. But I ran a few checks. All of the lovely psychopaths I've been working with since starting my PhD are present and accounted for. I also checked Broadmoor's records. No recent releases that were likely to have been involved in this… okay," she said, seeing his expression. "I'm sorry. Call Hayley and tell her to stay put, and we'll go and pick her up, okay?"

As Lestrade pulled his phone out, it spontaneously started to ring. He flung it onto the floor as if it had been a snake and covered his face with his hands.

"Greg…?"

"It's June Merivale," he choked. "She's been calling all morning… I can't, Mel, I just can't…"

Melissa reached down to the phone, picked it up, and killed the ringtone. "Okay," she said gently, laying her cheek against his shoulder and listening, for a few seconds, to the thud of his heart and the slight wheeze of his breath.

"Sorry..."

"Shut up, Greg. You've nothing to be sorry for."

The phone in her hand started ringing again. Grimacing, Melissa put it to her ear.

"Detective Inspector Merivale, is it?" she said down the line. "Dr. Melissa Brennan, Greg's fiancee. Yes, he's here… No. We're on our way to pick up his daughter… absolutely not. We will come back and see you about this issue in…" She flicked a look at the digital clock on the dashboard. "Give us ninety minutes. We'll see you then. Stop calling."

She threw the phone into the console in disgust and twisted the key in the ignition again. "Museum?" she suggested quietly.

He nodded.

"Do you want some time to calm down first?"

He nodded again.

"Okay." She checked her shoulder, then merged again into oncoming traffic. "I'm dying for a cup of coffee. I think you could do with some, too."

This time, there was no reply. The only sound in the car was the rhythmic squelch of the windscreen wipers.

~~o0o~~

John, arriving at Scotland Yard fifteen minutes after Lestrade and Melissa left it, got Charlie out of the car with misgivings. Even though they'd resorted to once taking her to the Barts morgue when she was seven weeks old, Charlie was not permitted into the third-floor lab where her mother spent much of her work day. He doubted their forensic lab was going to be any safer for a toddler than Barts'.

"Please behave," he muttered to her as he locked the car and hurried toward the front doors. "There might be chocolate in it for you…"

After a short trip in the lift, Anderson was in the corridor waiting for him. John had expected him to be wearing a lab coat and possibly latex gloves as well, but he was dressed down in a blue cotton shirt and jeans. He glanced dubiously at Charlie as the lift doors shut behind them.

"Sorry," John said ruefully. "She won't touch anything. What's going on?"

"You've still not been able to get hold of Sherlock?" Anderson tried.

John shook his head. For a second he felt a flash of injured pride, until he remembered that he'd prefer Sherlock to surface sometime imminently, too. Surely Matthew couldn't be that hard to find…? Sherlock knew every inch of London, or seemed to. He'd found a ridiculous amount of missing persons over the years. He was better than a bloodhound. What the hell was taking him so long?

Anderson led him not into the sort of laboratory he expected, all vials and tubes and acrid chemicals, but into what looked like a board-room. Flicking the fluorescent lights on, he went over to a long table lined with ergonomic chairs, where a number of crime scene photographs lay spread out. Shifting through them, he handed one to John. "I thought this was odd," he said as he handed it over, furtive but eager. "But I didn't know why at the time. The crime scene at Thompson's. Do you remember there was a puddle of vomit on the floor?"

John frowned. "Just the one?" he said lightly, peering at the colour image in his hand. "I remember the smell. I'm not surprised, though. If he'd been dunked under more than once, it's likely he'd have thrown up in between."

"That's what I thought," Anderson said, handing over another photograph. "But the reason I thought it was strange was because it was a neat little puddle, and all the way over near the window…"

John looked up from the photograph. "Like he was standing still?"

Anderson nodded. "Not the sort of thing I was expecting. So I've been doing some tests. You're right – Thompson vomited on himself. But the vomit near the window was a completely different sample. From a different person, I mean."

John raised his eyebrows. "You think the murderer did it? The murderer vomited at the crime scene they created?"

"Apparently."

John was silent for a few seconds, puzzling this out. "Can you get DNA from vomit?" he finally asked.

"Probably."

"Probably?"

"The sample's old, so it'll be harder than if we'd rushed it in straight from the scene. If I can get a profile, it might take a couple of days. And it's only good if we have something to match it with. But it's something."