"You have named the reason precisely, yes."

"I approve," says Bella. "All right. I'm going to finish crossing this neighborhood and then go home, sit very still on my porch with a book and a booklight and play 'I am bait', and I suppose you're now provisionally my escort for same."

"I sense a slight difficulty with the latter stages of this plan," he says. "But all right, as you like."

"You don't necessarily have to be on the porch, you could be a bit farther away," says Bella. "Unless that cramps your style." She pulls out a screwdriver and scratches a cross into a fire hydrant. "Do you have a bodyguarding style or are you making it up as you go?

"My style is as follows: I am extremely observant and ludicrously good at killing things," he says. "I shouldn't have any trouble lurking in a nice comfortable shadow nearby."

"There you go, then. How did you get to be ludicrously good at killing things? By your accounting you're six - seven? - years old. Even if you started working on it as soon as you could walk..."

"I am a genius," he says matter-of-factly. "An analytical genius, specifically. And I took all the martial arts lessons I could find once I picked my name."

"And you picked this one and not, like, Nick Stark or something obvious like that, because you are an analytical genius. I see," says Bella. "I've been watching aikido on the internet a little but I'm sure I'd give myself away as something supernatural if I tried to take lessons now - and before, I couldn't walk across a flat surface without tripping so I would have been taking my life into my hands. If I decide that you can be allowed within arm's reach of me I might require lessons."

"I would be happy to oblige."

"Very nice. By the way, if Charlie, my dad, should happen to notice you, I consider him entitled to any information he thinks to ask for, and he may also simply recognize you. He trusts me, but it's not impossible he will shoot at you before I can explain your presence. If harm comes to him - regardless of whether he starts it - that will permanently destroy your chances of... well, anything, teaching me martial arts certainly included."

"I will not harm your father," says Sherlock. "Regardless of whether he shoots at me. If he manages to hit me, I may have to shake his hand."

"He's a good shot and bullets go faster than bolts. Really?" asks Bella, intrigued. She paints a cross in a crosswalk and tucks one under the courthouse's drainpipe.

"I did not dodge your crossbow bolts by watching you shoot them. I dodged by watching you be about to," he says. "When someone is about to shoot at me, I arrange not to be where they are aiming. I evaded a probable assassination attempt that way as a human, in fact."

"Interesting," says Bella. Paint. Scratch. Tuck. Scratch. "I figured I had to be telegraphing somehow."

"You were. Nearly everyone does," he says. "To me. And I say 'nearly' only because I have not seen enough examples to make me fully confident of 'everyone'."

"Can you teach me not to, or are you sufficiently exceptional that if I'm letting you teach me anything I'm already covered?"

"Teach you not to telegraph to me? I doubt it most sincerely," he says. "Teach you not to telegraph to other people? Likelier."

"Am I that bad?" she sighs. "I do usually hit. Not always the heart on the first try, but I do usually hit."

"You're not bad," he says. "You're still a Slayer. But a Slayer without formal training, which is certainly not optimal, and merciful heavens I have just convinced myself to be your Watcher. What a night."

"Is that what Watchers are supposed to do?" Bella asks, strolling down the sidewalk. "Teach Slayers not to telegraph their shots? Because it sounds to me like their job is... watching. But perhaps that's an artifact from another time."

"The history of Slayers in brief, from what I have gathered since the subject became of interest to me: Back in the mists of time, some group of beleaguered humans decides to invest supernatural abilities into a champion who will defend them against the forces of darkness. For inscrutable reasons, they pick a teenage girl and design her portfolio of handy talents so that it will pass to some other teenage girl when she is inevitably killed in the line of duty. Then they train her up and send her out. The succession of teenage girls thusly empowered becomes a global phenomenon: Slayers. The Watcher's Council springs up at some indefinite point and makes it their business to track down a new Slayer wherever she might appear and assign a crusty old fellow to stick by her side, train her in the various arts of combat, and point her at evil things that ought to die. Why they call themselves Watchers, I haven't a fragment of a clue."

"I am sincerely uncertain if I wish I had one of those or not," muses Bella. "I don't suppose they'd give me a selection of crusty old fellows to ensure no personality conflicts."

"I am sure we can arrange to circulate rumours of your presence," he says. "They will pounce on you like starving dogs. I don't recommend it."

"The pouncing does sound unpleasant," she agrees. "Are they very disconcerted by my failure to appear on whatever manner of radar they have set up?"

"Headless chickens," he says. "I stumbled on one in my quest to find a Slayer, which I have since abandoned, largely because they could not find her either. Lucky me."