Andrew Stockton is an ugly man, thick lipped and greasy-complected; he has killed three teenage girls in a grotesque fashion, and raped them both before and after their deaths. He removed a portion of one girl's quadriceps muscle, and most likely ate it.
Andrew Stockton's gun is a small, snub-nosed revolver, old and poorly maintained; he used it as a threat mostly, but he did shoot the second girl in the leg when she attempted to escape him, which had been the clue that exposed all.
Andrew Stockton grins when Sherlock stares at him down the revolver's sights. "Go on," he says, eyes bright. "Do it. I'm an animal, put me down."
Sherlock adjusts his stance, not allowing the gun to waver. "Not really my area. The police will be here shortly, though."
"You're afraid of me, aren't you?" Stockton hisses, eyes small and watery and bright. "You saw what I did to those whores. You're afraid I'll do it to you."
"Hardly," Sherlock says. "I fall rather outside your victim profile, being both too large for you to easily overpower, and male."
"Look a bit girly, though, don't you?" Stockton says. "Fancy suits, pretty hair. I could broaden my horizons."
"You are tiresome," Sherlock tells him.
Stockton grins. Blood from his split lip runs down his face. "Then kill me."
Sherlock shifts again. The angle of his arm is rather uncomfortable. "To kill everyone who irritated me would needlessly complicate my social life."
Stockton's laugh is loud and grating. "It's all in the timing, though," he says, as though giving Sherlock a bit of friendly advice. "Fr'instance, just you and me here--nobody has to know."
"The hole in your head and powder burns on my hands would be rather difficult to explain," Sherlock points out.
"Tell them I came at you," Stockton suggests, shifting higher on his knees. "Tell them I was crazy. That's what they say about blokes like me, innit? Crazy."
When Stockton shifts, Sherlock takes the gun in both hands to keep it steady. "I don't particularly care about your exact diagnosis."
"You could tell them I came at you, though," Stockton says again.
"The details of the entry and exit wounds would reveal that I was lying," he explains, loudly, even while thinking that for Scotland Yard to notice that would be an unexpected stroke of genius.
"And good boys don't tell lies, do they?" Stockton says.
They stare at one another. For a large, thick-bodied man he moves quickly--too quickly--in the space of one infinite heartbeat Sherlock sees Andrew Stockton coming at him, hands still tied behind his back, mouth gaping shark-like, wide and inhuman. His hands are tied behind his back. He has bitten off various pieces of three different girls.
A gunshot stops him, but the revolver is still cocked, fully-loaded, heavy in Sherlock's hands.
It is harder to explain this time, how exactly a bullet from a Sig Sauer P226 ended up in a man's chest, but Sherlock discovers that mumbling Moriarty and looking grim has a very nearly magical effect. John was, of course, on the other side of London at the time and nothing to do with this particular case and also doesn't own a handgun, what are you talking about?
"Do you feel sorry?" Sherlock asks him, later that night.
John is eating—tinned spaghetti that he warmed up in the microwave after clearing it of tissue samples—and he chokes a little bit and turns to look at Sherlock, who is laying on the sofa with his legs against the wall and his head hanging off the edge of the cushion. "About Stockton?" he asks, as if Sherlock would be asking about anything else.
"Any of them," Sherlock says, for that's three people John's killed in civilian life: Stockton and the cabbie, and a nasty little thug in a drug-smuggling case. He didn't shoot the thug, either, just slammed his head into a cinderblock wall and left him on the pavement, bleeding out inside his brain. Before, in the army--who bothered to count?
John goes very quiet. "I don't think sorry is the right word for it," he says eventually. "Because you don't get into a fight if you're not willing to end it, one way or another. You don't point a gun at a man unless you're already prepared to shoot him."
Sherlock thought he was prepared to shoot Stockton, because Stockton was--well, an animal. A particularly creative and entertaining animal, with a few clever tricks, but ultimately a subhuman, a thing, a puzzle already solved. Sherlock thinks he could shoot Moriarty, too—and feel disappointment for destroying that great intellect, but no particular remorse. He wouldn't be sorry about it.
"Because he's not a very nice man," Sherlock says.
John doesn't seem to recognize his own words flung back at him. "Because sometimes that's what it takes. Sometimes that's what you choose, and you don't--you know what you're doing and you decide it's worth it."
Such rapid moral calculus, from a man who can't even remember phone numbers with particular accuracy. "Does your own capacity for violence ever frighten you?"
John frowns. "I've got to stop letting the murderers talk to you."
"That is not an answer to the question."
"No, then." He turns back to his plate. "I do what I have to."
This calm assessment--this untroubled conscience--it had intrigued him, after the cabbie. John is calm under pressure and acclimated to violence and can sleep well after shooting a man. Sherlock remembers looking at John after the cabbie and wondering if he'd encountered someone as cold and distorted as himself, someone else the therapists would stick a label on if only they could see past the smile and the light-colored jumpers.
Now he wonders if he knows what label to stick on himself.
"Is this about Stockton?" John asks. "Does it...I mean, he was a monster."
"He was going to hurt you."
"I had his revolver."
"I couldn't see it from where--"
"I didn't shoot him."
There is silence in the flat. Sherlock shuts his eyes, and listens--the click of flatware, the squeak of the chair. John's footsteps, never entirely even, stopping. "So either you're cross at me for getting him first, or...?"
"I had no reason not to," Sherlock said. "No reason at all."
John sits down, and Sherlock opens his eyes: from this angle the doctor looks tall. "Not everybody's capable of cold-blooded murder, Sherlock. There've been studies--"
"I am familiar with the studies," Sherlock said crisply.
"Then you know the metaphor," John said. "Sheep, wolves, sheepdogs. The sheep can't harm someone except maybe by accident, crimes of passion--that's ninety-five percent of people. The wolves--"
"Sociopaths," Sherlock says, and the word is too loud in the room.
"Ah." John smiles faintly. "Did you ever really believe that, though?"
"It was a comforting illusion," Sherlock mumbles.
John shakes his head. "I'm not judging you. I don't think anyone at the Yard would judge you. Some of them might actually be relieved, to tell you the truth."
Sherlock looks at John, who shot a man today and is teasing him now, is eating spag bol out of a tin for dinner, is a good man. "Sheepdog," he says, and bumps John's shoulder with his knee.
John rolled his eyes and pokes Sherlock in the ribs. "You seem to need one."