It's a quarter to four in the morning. They've been up three--well, four for Sherlock--straight days, chasing a serial killer who'd been leaving clues in crosswords mailed to the Times. They'd found him in Hampstead, of all places, held him at gunpoint for nearly an hour until Lestrade showed up.
Brilliant work on Sherlock's part and none too shabby on his own, if he does say so himself, but now they're just trying to get home before they collapse. John's honestly not sure they're going to make it. He drops his head back, to conserve his strength, and pulls his jacket tighter around him.
He hasn't the faintest idea where they are. At this time of night, even London is quiet. After three days of pacing around the flat, racking his brain and flinging words hopefully at Sherlock, John feels he's tumbled into a world beyond language. There's a yielding coldness behind him, something hard against his feet, a faint sharpness in the air, and he doesn't have the words for any of it. If someone pointed a gun at him right now, he's not sure he could produce name, rank, and serial number.
He lets his head fall to the side, in Sherlock's direction. Sherlock's trying to sit up straight, but his head sways with every movement of the cab. It's dim in there, but not truly dark; the lights and shadows of the city slide over them smoothly, plunging them in and out of a black and white film. Picking out a half-closed blue eye over a shard of cheekbone. Two gloved fingers resting languidly against glass, a second from sliding down. A corner of mouth, curving down into darkness. One moment grotesque, another otherworldly.
"Three across," he says, abruptly, but in a blurred voice, as if he's talking in his sleep. John's not even sure he knows he's said it out loud. "Three across."
The knowledge that it's from the case, one of the few clues they hadn't gotten, reaches John after some immeasurable lag. But the case is over, they've left it behind, with Lestrade and the flashes from the camera and the forensics team crawling over every inch of the place. Now they're here, and it feels to John as if they've fallen right out of reality, floating along the current of some endless night which they alone inhabit. Just the two of them, spinning and dipping and at any minute they might slip right under.
That's probably why John puts a hand to Sherlock's cheek. The skin is chilly and a little dry and he says, "It's over, Sherlock, we're done."
And that's probably why, after a minute, Sherlock breathes out and turns his head into John's palm. His eyes go almost all the way closed, and he mutters something else incomprehensible.
John's exhausted, he can't keep his arm outstretched like this, and so he just gathers Sherlock in. There's a vague surprise on Sherlock's face, but it's easy, no resistance at all. Sherlock's head lodges against his chest and his coat spills over John's knees. Sherlock never wears cologne, but John registers the weight, the warmth, the textures of wool and cotton and leather; they flood his awareness, leaving no room for anything else, like thoughts about whether this is inappropriate or just really strange.
"Mmmf," Sherlock says after a while, but with a small smile, as if he were telling a secret to a child. John wonders what would happen if they both fell asleep, right there. Would the cab drive them around forever, keeping them suspended in this mysterious little world?
"Mmmm," he says back, and kisses Sherlock's hair like it's the most natural thing in the world to do, the thing that requires no thinking at all. Sherlock makes a contented little noise in his throat and burrows in closer. Some other time, this might trouble John for some reason he can't remember right now, but all lines of reasoning have slipped from his grasp.
Safe. It's less a word than an instinct, a deep conviction that hums through him like the rumble of the motor, like the beating of Sherlock's heart. London is safe and the victims are safe and Sherlock is safe and it's all right now, he can sleep. He's looking at the light advancing and receding over Sherlock's hair like an aimless caress and then he's seeing nothing at all.
He dreams of three across, and, deeper still, the word concordant, but when he wakes to the early blue morning and Sherlock dazedly handing money to the driver, it's gone.