Tom was being stroppy again. Sherlock seriously considered putting away the diary and leaving him to stew, but that would mean he'd have to actually listen to Lockhart's lecture, and that would no doubt end with Lockhart resigning and himself being expelled.

"You must be mad!" Tom was still going on. "What do you mean, it just slipped out? You recited your Potions Master's entire life story to a class full of children!"

Sherlock scowled.

"You sound just like my brother," he wrote. "You ought to meet him sometime. Or perhaps not – I expect he'd shut you up in a government facility and experiment on you. Anyway, I didn't tell them everything, I left out the bit about Snape being a double agent – "

"Oh, for Merlin's sake!" Tom interrupted. "What's the use of being able to read someone's life at a glance if you just use it to make them angry?"

"Well – "

"Don't answer that!" Tom's writing was spiky with annoyance. "You cannot just go about insulting people. You'll never build up a following that way!"

Sherlock rolled his eyes. "I don't want to build up a following," he replied. "It sounds so dull."

"Don't be ridiculous," Tom returned. "Everyone wants to be listened to."

"I don't," Sherlock replied. "People are stupid, remember? Imagine spending all your time ordering them about. You'd wind up all fat and boring like Mycroft."

There was a long pause.

"I suppose," Tom said at last, "that you would prefer them to order you about instead?"

"Of course not," Sherlock replied. "I don't want anything to do with them at all." Well, that wasn't entirely true, so he added a clarification: "Unless they're dead, of course."

There was another pause, the longest yet. Sherlock frowned. He'd dismissed his malfunctioning-magical-diary hypothesis long ago - but perhaps he had managed to overload the thing somehow?

Finally, letters slowly began to appear:

"How…remarkable. Do tell me more."

Sherlock shrugged.

"Not much to tell," he wrote. "I've been getting the Prophet since I got my Hogwarts letter, and there hasn't been a single decent murder in all that time." He frowned. "You would think that a hidden civilization that carries around death weapons would manage to come up with a few interesting crimes –"

Tom interrupted, his writing slightly shaky, as if he were in the grips of some strange excitement.

"Perhaps…you would like to…rectify that situation?"

"What?" Sherlock blinked. Then he rolled his eyes, trying to ignore the little stab of disappointment. Tom might be cleverer than most people, but he had made the same mistake as all the others…

"You've got it all wrong," Sherlock wrote. "You think I'm some sort of psychopath, who likes hurting people up for fun. I'm not." He punctuated his sentence with a fierce jab, then continued. "I'm a high-functioning sociopath."

There was a pause, and then the letters appeared almost reluctantly: "What's that when it's at home, then?"

Sherlock smiled. Tom hated not knowing things.

"A sociopath," he wrote, "has little to no ability to empathize with others or feel remorse for his actions. He treats people as his playthings, to use and discard as he sees fit. A high-functioning sociopath is the most dangerous of all, as his great intelligence permits him to move easily in normal society."

There was another, longer pause. "Is that your own assessment?" Tom asked.

"No." Sherlock narrowed his eyes. "School psychologist's." Dr. Golwich was a thin, middle-aged man with a receding hairline and three cats that he was allergic to (they belonged to his wife, who refused to get rid of them). He also had a longstanding and unsatisfying affair with the choir-mistress, an undiagnosed cardiac arrhythmia, a bottle of whiskey that he kept hidden in his bottom left desk drawer, and he had spent the entire appointment talking to Mummy as if Sherlock wasn't there.

A pointless memory, but somehow he had never managed to delete it.

"Remarkable," Tom said. "Tell me, what is your interest in crime, if you do not wish to be a criminal yourself?"

"It's obvious, really, but you haven't got a brain so I'll be lenient. I'm going to be a detective."

"Are you indeed." There was a pause. "They are known as Aurors in the Magical world, though I cannot imagine why – "

"They're known as absolute idiots to anyone with any sense!" Sherlock retorted. "Honestly, they have no investigative capabilities whatsoever, they think they can solve any problem by throwing a stunner at it, and they haven't put out a single textbook on forensic Magic." He paused, frowning. "I suppose the quality of police work is related to the caliber of crime. Though they'd be in a nasty spot if a real criminal came along – "

"Oi!" Sharp fingers dug into Sherlock's back. "Class is over! We've got Charms now!"

Sherlock looked up. Books and papers were strewn everywhere, students were carefully emerging from under desks, and the air was filled with tiny, shrieking blue creatures. Lockhart was nowhere to be seen. Sherlock sighed and gathered up his things.