A/N: written for a prompt on sherlockbbc_fic.

n. A mistake made in ignorance.

They have T-shirts. 'I shared a flat with Sherlock Holmes and lived.'

(And of course, there's the one who was wearing 'I shared a flat with Sherlock Holmes and died' at his funeral. The two events were not directly correlated. His mother was just a bit... odd.)

They have a support group. Well, they call it that. What they mean is, all of them wear their T-shirts and meet up in a pub on the first Saturday of the month. They get pissed and share horror stories of the body parts in the kitchen, the violin concerts at two a.m., of pulling a book from a shelf and finding the skull leering behind it, of never having a single thought to yourself.

It was the last that did it for Edward. "I just couldn't take it, y'know?" He'll say, every time. "Jesus, fuck, I just want to have a little privacy in my head, alright? s'too much to ask?"

All of them will nod-nod-nod like that bloody dog from the Churchill ad.

"I got used to the skull," Victor told them once, shot glass glued to one hand. "Hell, eventually, I started to talking to it as well. Called it Theodore. Don't judge me," he wailed, because even knowing Sherlock Holmes, they were judging him.

"So I got used to the skull," he'd said defiantly, after his shot glass was refilled. "It was a better flatmate than bloody Holmes."

Nod-nod-nod like the Churchill dog.

"But then I go to the bathroom one day, and there's a fucking corpse in the bath. Not a hand or a foot or an ear, y'know, the usual. No. A whole fucking corpse, artfully dissected."

It's pretty bad, that miscellaneous body parts are 'the usual'.

"I was young and stupid," Tom says.

(They've all got the same basic story here: young. Foolish. Thought the first meeting was an aberration. Triumph of optimistic stupidity over instinctive run-like-fuck.)

"Needed a place to stay, couldn't afford it on me own, thought the guy looked like a laugh-"

Incredulous looks all round that say 'god, you were stupid, weren't you? I'm not sure words exist for that level of stupidity'. Normal people wouldn't look at him like that. Normal people, dealing with their pale imitations of the True Flatmate From Hell would accept that as an excuse.

But they've all shared with Sherlock Holmes. That's the point.

"He read my miiiind!" Tom wails. "Could tell when I wanted to shag someone just by the way I blinked."

'Possible sexual identity crisis' is the thought that travels round the table. 'Couldn't deal with having it pointed out'.

But: nod-nod-nod.

"The violin," says Johnny darkly.

"The violin," the table dutifully echoes in response, a soft doom-laden whisper.

"He does it on purpose," Alex says. "I heard him once, when I got back early. Played like an angel. An angel with a violin, that is. But no, two a.m. in the morning, nothing but screeches like a cat in heat."

"I hear he's tricked another," Ann says. "An injured war vet an' all."

"Poor man," they murmur. "Poor fool."

"Raise your glasses," Victor says drunkenly. "To our soon-to-be-member, John Watson!"

"John Watson," they solemnly reply.

They keep waiting for John Watson to join them.

He never does.