They arrived at the police station some forty minutes later. It was still barely past one o'clock in the morning, though to John it felt much later, as though the sky was about to fade into morning at any moment. There were still a few Saturday night lingerers in the street—a couple of young men with gelled hair and leather jackets; a blonde girl in a thin green dress, limping along in heels that looked like instruments of torture. The front doors of the station were, curiously, unlocked; Sherlock and John went in, directly up the stairs to the squad room without being challenged until they actually got to the door. There they found an officer standing, hands folded, not-quite at attention, as though he was guarding it. John recognised him as the kind-faced officer he'd first seen when they had discovered Derek Metcalfe's body, or what was left of it.

"Go in," he said through his teeth, gaze fixed over John's shoulder at nothing in particular behind him. "Cells are through there on your left."

"What happened?" John asked him.

"Brian Stern happened."

As soon as they saw him, standing behind one of the desks in the squad room, it became obvious that something had happened to Brian Stern, too. He seemed ruffled, like a rooster who'd just got into a scrap, tie askew, thinning grey hair dishevelled; he had a handkerchief to one corner of his mouth, and his moustache was flecked with blood. "Watson," he said, and he didn't look pleased to see him. "I don't remember calling you or your friend in."

John stopped. That sneer, that faint homophobic threat; not only that, it had not yet occurred to him that he was going to need to invent an excuse to be there that didn't incriminate the officer at the door. "Yeah," he said slowly, "Yeah, the um… the thing is…"

"Dr. Watson was just after some of his case notes," Sherlock finished for him, hands behind his back, as if he owned the place and was inspecting it. An easy task, John thought, for a man with an accent like Sherlock's. "I wanted to examine the photos of Metcalfe's injuries again, in case it revealed any clues—"

"Yeah, I didn't ask for your life story." Stern sat down with a little grunt of effort. "Well, you may as well know, we've got a real pain-in-the-arse prisoner in here tonight."

"Lestrade," John said. "What did you arrest him for?"

"Pretending to be a detective and interfering with an active case."

"Don't be ridiculous," Sherlock broke in sharply. John, glancing at him, saw he had an odd expression on his face; if he didn't know better, he would have thought it was guilt, bordering on remorse. Did Sherlock even have emotions like that? "I was with him yesterday morning," he went on. "We were interviewing Sheila Noonan and her sons about Metcalfe's case, and she took offence at his line of questioning—"

John was barely listening now; instead, he watched as the secure door to Stern's left opened and the sharp-featured police officer, whose name he still didn't know, emerged. He also seemed in a state of disarray, and his right hand was wrapped in a towel.

It was just possible that the insistence that Lestrade might be killed was an exaggeration, but the more he stood in front of Brian Stern, the more John doubted it. Stern had clearly been in some sort of fight—punched in the mouth, judging by the location and severity of his split lip—but the knuckles of his hand weren't damaged. Lestrade had probably been either kicked, stomped, or hit with an object. An object that could have been anything from a phone book to a nightstick.

"Let me into the cells," he said to Stern, cutting Sherlock off. "I'll take a look at him."

Stern raised one eyebrow. However convincing Sherlock had sounded about their quest for crime scene photos, he was clearly no longer buying it. "Will you now?"

John held in his exasperation, but barely. "Yeah, I will," he said. "I don't know what you've done to him, but I'm going to find out eventually, so you might as well save us both some time and cooperate."

"Says who? You're not going in there to nursemaid him, he's under arrest," Brian said.

"Oh, don't give me that," John said. "My job is to tend to detainees. Give me the bloody keys to that cell right now or you won't like what happens next—"

"Inspector Stern," Sherlock said politely, "Does Commissioner Allen know about Alfie Margent?"

Stern stared at him in silence. His eyes, normally a pale, oysterish blue, had suddenly dilated so that they were nearly black. "What?" he snapped.

"Oh, I was trying to be polite," Sherlock said, looking him over with a kind of disgusted superiority. "I'll try to simplify it to your level of comprehension, but there are no guarantees: Does Commissioner Allen know you've been taking bribes from a known criminal to look the other way over the fact that his nightclub is a front for organised crime?"

The cell was dark when John unlocked and opened it, and it was hard to make anything out except that Greg Lestrade was sitting on the floor in one corner, knees up, head tilted back against the wall. That alone was cause for concern. God knew how filthy the floor of a holding cell was, and surely Greg knew it, too. The last thing he should have been keen on doing was sitting on it when there was a perfectly good bench seat beside him. Except, John thought grimly as he found the cell light and switched it on, you can't fall off a floor. The fluorescent lights flickered to life.

Lestrade's face was a mask of blood—dried dark in some places, still flowing in others. One eye was closed—it was unlikely he could open it if he'd tried—and his blue police-issue shirt had patches of dark grape-purple on it. Several of the buttons were missing, and the seam of one shoulder had been ripped. Appalled, John got down on the floor beside him, giving his shoulder a little shake. "Greg?"

"Mmm," was the response. Lestrade put his battered hand up to brush his hair off his forehead, wincing. "Yeah, calm down, 'm fine," he said, voice so thick he was almost unintelligible.

John got to his feet. "We're leaving," he said to Stern, who was watching them from the cell doorway. "And we're taking him with us."

"Which part of 'under arrest…'"

Abruptly, Sherlock rounded on him. "You have made your point," he snarled. "And we're leaving."

For all that Sherlock had been next to useless during most of his dealings with Brian Stern, John had to admit that he was handy at the next challenge: getting Lestrade down the twenty stairs to the front lobby and out onto the street. Only there, under the bluish street lights, was he able to have a proper look at Lestrade's injuries. Sherlock was uninterested in this; once he'd propped Lestrade against the concrete wall of the building he wandered to the corner, on the lookout for a cab.

"Okay," John said, after a minute or two's appraisal of Lestrade's face. "Have to tell you, I'm relieved. The last guy I treated who'd been punched in the face had his jaw hanging off. But you do need to go to a hospital."

"Nah," Lestrade said. He'd refused to meet his gaze, instead watching Sherlock instead as he made his way back from the corner, hands shoved into his pockets.

John had foreseen this protest. "That's not a suggestion, Lestrade. You have to—"

"He can't," Sherlock said, having just reached them.

John stared at him. He'd have expected Sherlock to refuse medical treatment for any injuries he might have sustained—after all, he'd been bruised and battered himself when the bomb had gone off in Baker Street a few days before, and even Mycroft hadn't been able to convince him to seek help for that. But he had no idea why Sherlock would care enough to intervene on Lestrade's behalf. "What's got into you?"

"Can I see you privately?"

Sherlock led him to the street corner and John followed, watching as Lestrade leaned, exhausted, back against the wall where they had left him. "What the hell?" he asked again, once they were out of earshot. "Are you blind? He'll probably need to be admitted in that state."

"And if they admit him and ask questions, he'll almost certainly lose his job, or the beatings will get worse, or the beatings will get worse and then he'll lose his job," Sherlock said, as if he were trying to explain rocket science to a particularly stupid child. "Have you never been bullied?"

John had at one time, since he'd always been smaller than the other boys, but he hadn't put up with it for long. "Since when did you care so much if he's bullied?" he demanded.

"Since my life depended on his remaining on the police force until 2010."

For a moment, John was silent. Then he blinked. "Sorry," he said, "run that one by me again?"

"I've been thinking," Sherlock began.

"I can tell—"

"Shut up and listen to me. I've been thinking. You told me people are always thrown into parallel dimensions—time travel, if you want to call it by its inaccurate name—to right a wrong or prevent something from happening or make sure it does. We were at the point of being blown up at that pool, if you've forgotten."

"I haven't," John said.

"The very point, the crisis, half a second into that explosion, and suddenly we're here, assisting Lestrade with a case. A case where the outcome might well mean the difference between his staying on the police force or not."

John grappled with this. Sherlock was a genius—so much had been obvious throughout the two months they'd known each other—but now he was beginning to seriously entertain the idea that he was a mad genius instead of just an abrasive and eccentric one. "So, what," he said, "you think he's going to come save us at the sports centre?"

"One of us, anyway," Sherlock said. "You were up against the change-room stalls when the blast went off, remember? So whatever we're here for, whatever it is, we need to keep Lestrade on the force. And that's not going to happen if there are professional repercussions for tonight's events. We need to keep him away from A&E and from anyone else who might influence him to quit his job."

"That stuff," John said, "that stuff you said to Stern about Alfie Somebody. It was true?"

Sherlock nodded. "Lestrade told me once. He said Margent was the kingpin of organised crime in Bristol when he was there, and, true to form, it took him four years to find out the police were taking Margent's bribes to stay out of his business."

"Then we can just blow the whistle on that and get Stern fired. And then put in prison himself."

"Yes, in a few days. In the meantime, we can't shine a spotlight on this department. We're on the verge of solving this crime, and now we have that leverage over Stern, he'll not only back away from Lestrade, he may also allow us access to any notes we ask for."

"Or he'll just send a few officers to have you beaten to a pulp as well."

"I'd like to see them try," Sherlock said, aggressively humourless about the prospect.

It was almost dawn before the three of them arrived back at John's flat—after some debate on whether it would be easier to take Lestrade back to Broad Street—and it took John's reluctant patient a good five minutes to get from the kerb into the building and up the two flights of stairs. Which, John, decided as he unlocked the door and let his companions in, turned out to be a handy diagnostic tool. If he hadn't been certain at the police station whether Lestrade had broken ribs, he was now.

"Sit down," he said, pointing to the sofa that was currently serving Sherlock for a bed.

"Can I have a smoke?" Lestrade asked him plaintively.

"Over my dead body." John was in the bedroom now, pulling his medical case off the wardrobe shelf and onto the bed. He rummaged through it, returning to the sitting room to find Lestrade exactly where he left him and Sherlock standing nearby, apparently doing nothing. "Shirt off," he said to Lestrade, trying not to snap at him. It had been one difficult aspect of going back to work at the surgery with Sarah—he was used to speaking to soldiers and other military personnel, and you didn't play nice with them the way you did with ordinary members of the public; you barked orders at them. No doubt, he thought, Lestrade had had enough of that for the time being.

Lestrade peeled his shirt off one shoulder at a time, with irritating slowness, but John did not offer to help him, and waited in silence until he'd put it aside.

"Jesus," he said, not even bothering with his bedside manner now. There were grazes and emergent bruises on both sides of Lestrade's chest, but they were laid over healing bruises of pale green and yellow. John glanced up at his face again. Difficult to see under all that blood, but he remembered that shadow of a black eye, one of the first things he'd noticed about him. "How often have they done this?" he wanted to know.

"It's fine," Lestrade said.

"I didn't ask you if it was fine. How often have they beaten the hell out of you?"

Lestrade shrugged, taking in a sharp hiss of breath as his broken ribs clunked. "Once or twice."

"What'd you get it for last time?"

"Pulled over this guy," Lestrade said, wincing as he shifted his legs into a more comfortable position, "Driving like a bat out of hell, right in front of a marked squad car—he nearly hit a car in the next lane head-on when he cut the corner. So I put the lights and sirens on and pulled him over. I was only going to give him a warning, you know, tell him it's all fun and games until he hits a kid, but then he gives me a mouthful for pulling him over. Said he was Charles Hyde. That pissed me off, so I said I didn't care if he was God, and booked him."

"Charles Hyde?" John looked up at Sherlock for help.

"Assistant Chief Commissioner's brother-in-law." Of course, Sherlock knew that. After only two days, he apparently knew every soul in Bristol.

"Oh." John looked back at Lestrade. "Yeah, that probably wasn't your best professional decision. Judging from all that we saw tonight, the whole place is as crooked as a barrel of fish hooks, so the last thing they'd want is the Assistant Chief Commissioner breathing down any necks. So why do you put up with it?"

Lestrade shrugged again, more carefully this time. "How else am I going to become a detective?" he wanted to know. "They're not going to transfer me to Scotland Yard if I whine a lot about being picked on, are they. Aren't you going to tape my ribs up?"

John, who'd been planning on doing no such thing, blinked. "You've had broken ribs before," he said. "Did Stern or whoever break them last time, over this Charles Hyde guy?"

"Don't think so. But I definitely broke two playing football, back at school."

"Times have changed since you were at school, and so's medicine," John said, going over to the fridge and opening the tiny freezer drawer, hoping for ice—none of the groceries he'd bought earlier had been frozen goods. All the same, he located an opened half-pack of freezer-burned peas, pulled them out, and yanked the tea towel off the rung of the oven to wrap the frozen bag in. "Broken ribs won't kill you, but taping them's only going to put you at risk of pneumonia, which might," he said, handing it over. "Nothing much we can really do but wait for them to heal, I'm afraid."

Lestrade shut up then, except to wince as he dutifully hugged the makeshift cold-pack to his chest. Since there was nothing more he could do in terms of first aid without raiding the surgery or insisting on the hospital, John finally sat down in the armchair. The South Atlantic Medal was sitting on the coffee table, and he briefly wondered how it had got there—last he'd been aware, it had been in his jeans pocket.

"So," he said, trying to shift the subject, "did you actually find out anything good from Sheila Noonan, or was all that a waste of time that got you beaten up as well?"

"Peter Noonan is being molested," Sherlock said, almost too quickly, as if he were relieved that they were returning to a subject he was better at that anyone else. "His brother Jeff, too. Judging from the number of missing boys from this area, I believe we're dealing with a massive pederast ring."

"You think this is that involved?" Lestrade coughed into his hand, then winced in pain. "I mean, I knew we were looking for a sicko, obviously, but you think there's a whole ring of them?"

"Look at the facts," Sherlock said. "More than half a dozen boys have been abducted, and that's only the ones we know of. Who knows how many have been successfully overlooked or covered up? A lone predator wouldn't have the resources to run something so complex, especially since we know the boys aren't dying right away. Where is he taking them? He needs a place that's isolated and secure, a place which only he or his accomplices have access to, where he can't be observed coming to and from, especially if he's got the boys with him. Somewhere no-one can hear them call for help, or scream when they're—"

"All right, skip that part," John said. "So we're looking for a paedophile ring. How exactly do we go about finding one?"

Sherlock appeared to be giving this some deep thought. "There has to be a connection between the boys," he said, almost to himself.

"There isn't," Lestrade protested from the sofa. "I told you, Alan's not local and he only just got here."

"No," Sherlock said. "You said he got here on Sunday, that he and his sister spent the day shopping together, and that he went out by himself on Tuesday and vanished sometime during the day. So he had at least two days' opportunity for someone to find and target him. Perhaps he wanted to be sent out on Tuesday because of someone he encountered on Monday."

"I doubt it," Lestrade said. "He's an idiot, but he's not that stupid."

"That remains to be seen," Sherlock said. "His sister was with him all day on Monday, or so you say. I need to speak with her in the morning."

Lestrade hissed again. "She can't see me like this," he said. "She'll flip."

"Then she'll have to 'flip'," Sherlock said. "You're going to look bruised and battered about the face for at least a week, and we don't have that kind of time."

After a few seconds of consideration, Lestrade agreed with, "Yeah, I think we can agree Alan's life is more important than my face."

"Arguable," Sherlock said. "The good news is that I'm confident Alan is still alive, and probably the other boys, too. This killer's like a cat who plays with a mouse and is actually disappointed when it dies—"

"Sherlock, can we talk?" John glanced at Lestrade to see his reaction to being excluded, but there didn't seem to be any. He had pulled his legs up onto the sofa and was slumped over the throw pillows, one arm raised over his eyes against the overhead light.

Sherlock looked expectantly at him.

"I meant outside." John wondered wearily when it was going to be safe to assume Sherlock knew basic social conventions. He did, however, follow him onto the dark stairwell without further smartarse comment, where he promptly lit a cigarette himself.

"No obvious signs of concussion," he said, when John failed to speak first.

"Sherlock, for Christ's sake, stop trying to do my job for me. I didn't come here to talk about Lestrade. It's about… what happened tonight."

Sherlock took a drag of his cigarette and waited. But again John failed to put his thoughts together for a few moments. The night still felt as though it had been a dream. In the flat below, he heard a door open and close. Donna was awake.

"That officer who was at the door when we got to the station..." he finally said.

"Neil Findlay." Sherlock ashed his cigarette onto the stairwell. "Lestrade mentioned yesterday that he had a detective friend named Neil who was feeding him information on the case. Only he would have called you for help if Lestrade was in trouble."

"Yeah," John said. "I didn't know his name, but he was there with Brian Stern and another detective when they found Derek Metcalfe's body, when we'd just got here. So he's definitely assigned to this case."

Sherlock stopped dead, the cigarette dangling from his fingers. "I see," he said. "When we went in, he told you the cells were located to your left."

John nodded. "Lestrade's acting like I've been working with him for months, and so's Brian Stern. So why would Neil Findlay, who's on the same case as me, think I didn't know my way around the police station I work at?"