As soon as John got out of the cab and into 221B, he paused to take a few deep breaths and collect himself. It wasn't that he'd never seen this sort of thing before; child abuse was depressingly common, no matter where you chose to work. You got accustomed to it. But you never could get used to it. At least, he didn't. With most medical matters, you eventually learned to turn off horror and just work on whatever it was. He'd seen children who had been badly hurt in accidents, children with fatal diseases, infants with cot death. He'd been in the army, for Christ's sake; he'd had seen people blown up on the battlefield! So why was this the one thing he couldn't stop being horrified about? Maybe it was because it wasn't a matter of sheer chance. Most illnesses struck at random, like being hit by lightning. There was no way of predicting it, or anything one could do differently. But something like this only happened because someone had wanted it to.

After a minute or so, he felt calm down enough to ascend the steps and unlock the door. When he entered, the air in the flat was heavy with the smell of formaldehyde, and knowing that Sherlock was still at one of his strange experiments was improbably reassuring. John even managed to crack a smile when he saw Sherlock inside alternately typing on his laptop and observing a set of animal organs spread on the counter (thankfully, all of them were resting on pieces of wax paper).

"Which patient was the one that upset you so badly? And those are from a cow, not a person, so don't ask Molly why she let me have someone's internal organs. Not that it should be a problem in the first place; if someone's organs were taken out that means they were either autopsied or were an organ donor and even if neither were true they don't need them anymore anyway." Sherlock didn't even look up from what he was doing as he said this, and for some reason it felt so oddly comforting that John almost laughed.

Sherlock looked up then, giving him a half-smile. "I hope that makes up for whatever bothered you there."

"Not exactly, but thank you anyway." John dropped his wallet and keys on the table and sat down in the nearest chair.

"What was it?"

"You mean you can't tell just from looking at me?" He realized that had came out much more harshly than he'd intended, and added, "Sorry. It was just…that bad."

"It had to be something big to upset you like that."

"You're right. I had to talk to this little girl, nine years old. She was admitted through A&E for vaginal lacerations. Obviously sexually abused but refused to say who it was." John was surprised to see Sherlock's eyes widen slightly, almost as if he was horrified as well. Maybe he was. Murder was one of those things most people could imagine the motivation for, but molesting a child definitely wasn't.

"Why did they want you to talk to her? You couldn't have admitted her," he finally said.

"Lestrade and Donovan asked me to," John responded without thinking.

"Lestrade and Donovan? Why did they call Scotland Yard for an abuse case?" Sherlock's voice was strangely flat, as though he was trying to bite back a flood of anger. Was it because they hadn't bothered to ask him to help them? He really couldn't imagine another reason; Sherlock thought of crimes as puzzles to be solved, not as emotional events.

"Apparently there's been a lot of victims from the area of London she lives in. There was a case a month or so ago where a boy mentioned he'd been one of a lot of victims, so now there is an investigation on the presumption it's the same perpetrator in all those cases."

"How long does this go back?" His voice was still flat, but there was a storm beginning to brew in his eyes. "Do they know when it might have begun?"

"Ten years ago or so. They've checked out all the past offenders in the area, and apparently they've all been ruled out. None of the victims have talked – in fact, they all insist nothing happened. Whoever it is, he's got a real hold on all of them."

"But obviously something did." There was no mistaking it; he now sounded distinctly angry.

"Yes. There's no other explanation for the injuries. The only good thing is that if whoever it is doesn't live in the area, she could possibly go home with her father. We don't want to send her home to the same thing." Unable to help himself, John let out a sigh of frustration.

"Do the Yarders have any leads?" He moved away from the collection of cow parts and stood behind John's chair.

"If no victim talks there aren't going to be any, obviously." John turned in the chair and, with a sinking feeling, spotted that "happy day, I have a case now!" look in Sherlock's eyes. "And no, they're not going to call you. So don't start thinking about it."

"Why not?" This was beyond an angry tone. It was undiluted fury.

"They said it was too sensitive a matter. You know that you can be…abrasive…" He trailed off, unable to continue his line of thought.

"Will she still be in hospital tomorrow?"

"Sherlock! You can't just walk in there and start questioning her! Anyway, it's a Saturday, and I imagine her family will be there most of the day." John wished he hadn't brought the subject up. He couldn't imagine how Moira would feel being questioned by someone who never bothered with typical social niceties.

"I can most certainly do that. I am going to do that. My only question is whether you will be coming with me or not." Determination mixed with the fury, this time.

"Why are you so invested in this, anyway? You don't know the family and it's not even very exciting by your usual standards." Maybe by changing the subject he could get Sherlock off the idea of barging in there himself. It was unlikely to work, but he had to try.

"I am going there," he merely repeated. "If you are so worried I will traumatize the child in question, you may stay with me while I speak with her. If you think I have crossed a line, you may remove me, although I don't think that will be needed."

Well, if he's so determined to work on this, I might as well run damage control, John thought to himself. "All right. I will come with you and usher you out if you cross that line." Which would probably be after about five seconds.

Neither spoke for several minutes after that, and the silence hung in the air like the smell of the formaldehyde. Sherlock was the one who broke the silence, surprisingly enough, saying, "People always assume."

"Are you referring to the Yarders this time, or people in general?" John dared to ask.

"Both," he curtly responded. "Take away your assumptions and there are more places to work with and look in." After that apparent non-sequitur, he walked back towards the counter and started working just like he had before, like there had been no significant conversation in between. If this was a preview of things to come, John was not looking forward to tomorrow. But the die had been cast; there was nothing to do but wait. And perhaps that strange fury Sherlock had shown before would make this somehow work.