The night is quiet, London at peace. A light snow dusts the ground, sheets of treacherous ice. Only the occasional cab trundling down streets. Night is inaccurate, early morning. Three a.m. in January, faint illumination of streetlights, or soft light seeping through curtains. It could almost be a hundred years earlier, a misty Victorian city in gaslight.
None of these things cross Sherlock's mind, of course. He is blind to it all, focused on tracking the nest of slayers so recently moved in, John by his side, each guarding the other's back, senses keen and sharp, long-adjusted to this darkness. (Ten years, in truth, for Sherlock. Ten years of darkness, not an ounce of daylight.)
The slayers have split up, spread out, trying to track the city's vampires. (They've been successful already with some less careful, less scrupulous than John and Sherlock.) Tonight is the night that it ends. Forces have been rallied. The slayers may think they're in the right, but it's the vampires who protect this city from so much other danger. (It's the slayers' own mistake that they don't count the werewolves as especially dangerous, though werewolf slayers and healer hunters have moved in, too.)
They've been out here for hours, hunting, stalking, calmly killing. Sherlock's Belstaff is torn and there's a scratch down the side of his face, while John got stabbed in the arm with a silver knife. (Clearly someone didn't realise the lack of impact silver has on vampires. And that was his big mistake.) Sherlock estimates that they can reasonably keep at this for another four hours, if they have to. (There are, after all, some benefits to winter when one is undead.)
Both wishes that they don't have to stay out that long. After all, every hour they stay out increases their chances of being dusted.