They're jumped before they ever reach Holland Park, three slayers to both of them. Sherlock can't understand how they were ambushed, the wood poison creeping insidiously along his veins, blurring his mind. John cries out as a silver knife pierces his shoulder, wrenching through the muscle, drawing out memories of Korea. The wooden stake that bites deep into his thigh takes over all thoughts, banishing even the image of Sherlock doing battle from his field of vision.
Sherlock's hands are quite full, and he feels more than sees the encroaching dawn, feels it deep in his bones and knows that the odds of their getting home tonight drop with each moment that they spend here. The growing pain in his shoulder sears when his arm is wrenched behind his back. It clouds his mind, blinding him to John. He twists, kicks back, catches one of the slayers behind the knee and topples himself forward, hitting the ground hard with the slayers still at his back. In the ensuing melee he manages to free his good arm, reaching into his coat pocket and pulling forth a vial of peracetic acid. The glass almost slips from his fingers before he smashes it into the back of the nearest slayer, rolling free from his captors at last.
John is still struggling, the stake in his leg slowing him down considerably. Sherlock doesn't have time to focus on freeing him, knifing his own adversaries, one in the chest and the other in the abdomen, the third thoroughly distracted thanks to the acid.
But there're more slayers, and then more, surrounding him. A punch thrown, a knife slashing through delicate skin, biting, burning pain in his own belly. (And doesn't that quite seal the night?) Sherlock pulls it out, forcing it instead into the chest of the slayer behind him. (He always knew baritsu would come in useful in a fight like this.)
And then there's John. And in the mess of bodies and blood and would-be killers John is beside him in spite of his own wounds, somehow still standing and Sherlock feels as though they could survive the daylight together if they had to.
He swoops in, coat flapping behind him and plants a kiss to John's cheek in the midst of it all. Neither says a word, and the coat slips to the ground, freeing Sherlock to drive another kick into the face of a slayer. (Tall, dark, married with three children and a mistress and how can he possibly be deducing in the middle of this fight for their very lives?)
John's eyes meet his, wide and round as a strange, strangled cry gurgles out of his throat. Sherlock reaches out, desperate to pull the stake out of his chest and promise him it will be all right, they'll be all right, the morning will find them back in Baker Street. But his hand is a heartbeat too late and the dust that was John H. Watson slips through his fingers.
A slayer pulls his arm back, and Sherlock's mind is blank, seeming to short out and throwing the place into tumbling disarray. His teeth embed themselves in the slayer's throat, ripping it free as his body collapses to the ground. And the others are watching him now, this vampire, trapped like a feral animal in a circle of hunters, snapping at them, clawing, until some danger from behind has them dropping back, some falling, blood blooming on their chests or fountaining from their throats. Sherlock is oblivious, knowing only that John is gone, John is dust, ashes on the ground and on his hands, and somewhere a quieter voice in the back of his mind murmuring, the sun won't be long in rising.
The gunshots - Smith and Wesson pistol, very distinctive - reach his ears before the world speeds up again, bullets embedding themselves in his chest. And he knows, deep down he knows as the snowflakes still fall around him, that the bullets are wooden.
He sways, knees buckling and hitting the ground. It doesn't matter. John is gone.