"Is my new librarian a Watcher?" she asks Sherlock the day after Mr. Giles joins the faculty.
"You'll be able to tell by whether I wince or not when you come by and it is time to do this again."
"I suppose I'll have more precision available. I am starting to get tired but I'm not actually sure if that's physical exhaustion or it being late. There's no clock in here. Hang on a sec while I get my phone?" she asks, executing a throw that, if allowed to land, ought to send him flying into a wall and give her the leisure to do that regardless of permission.
"By all means," he says, remaining where he is.
She consults her phone. "Not quite bedtime, but close enough that it's probably a good place to stop and head home," she says. "You escorting me?"
They are not attacked on their way to her house. "See you tomorrow," Bella says cheerfully as she parks the truck and hops out.
She picks her Slayer skills apart. She finds things that do not make sense in among the good reflexes; the killer instinct, the subtle drop in self-preservation that she imagines was installed to match her regen. (She is not, happily, sore in the morning.)
And - like they are just waiting to be edited, like they know they are thousands of years old and must yield to training or more deliberate revision when asked in response to new contexts and techniques - they rearrange to suit her.
She grins. She doesn't think she can beat Sherlock when they fight again, but she thinks she can surprise him.
"Slayer instincts want to be patched," she reports. "Once I made up enough vocabulary to write about them, it was easier than not being mad when people interrupt me."
"I am delighted," he says. "Let's go and give your revisions the smoke test, shall we?"
"Do let's." She practically traipses to the crypt. Once there, she divests herself of excess baggage and attacks without further warning.
Sherlock grins.
He still keeps ahead of her, but now he has to work at it. Half speed will no longer do the trick.
Bella's shunted enough of her intelligence into her handy new autopilot that she can focus her immediate consciousness almost entirely on reading his body language and his attacks to tell it which patterns to pull out. She feels like nothing so much as a conduit between sense and motion: she sees this, and her seeing directly causes her weight to shift, her hand to strike, her foot to jut out just so and force him to dance away. All she's doing is keeping her eyes open, keeping her attention laser-focused on the fight, and feeling the feedback from every sense she's got.
"This is just what I was able to patch without knowing what I was doing. Feel like learning about thirty new vocabulary words and trying to read my notes-to-self?" she asks casually.
"Mostly just - well, for one thing, did you know that my self-preservation instinct was cut down to size for some reason? I didn't start wanting to throw myself in front of a train or at a demon nest, probably because I already wanted to be immortal and the change wasn't big enough to get me to regular, let alone sucidal, but it was there, which was... well. Interesting design choice. I left it mostly the way it was in the short term because I really don't need to be as concerned about injuries as I used to be - except brain damage, that's still a big deal - but I did not want that long term deathwish."
"I suppose they don't want their Slayers deciding that, no, fighting nasty bitey nightlife is scary and they'd rather take up knitting," says Bella. "This is, after all, a system that was deemed preferable to any option involving volunteers."