This is something new.
There's a curious tingling at the top of his spine that begins the moment he identifies Mary's voice downstairs—it takes all of two words but is a surprise nonetheless. The second thing that seeps up to him from below is the panic rising in her throat, and that's all it takes for him to figure out what's happened. The exact details are unimportant, but only one thing mixes fear and Baker Street in Mary Morstan's head.
Something is wrong with John.
He meets her on the landing, feels his mind sharpening, focusing in with a familiar, scalpel-like precision. Only now could she mention that skip code with such confidence and and pay no mind to the consequences of breaking her facade, if only for a moment. Only now could that information be registered and just as soon deleted in his brain.
He thinks later, of how much could have been prevented if he'd caught that. If thoughts of John bloodied and dying hadn't been invading his thoughts every few milliseconds, then he could have faced her with that disarming, deadpan look of his and dared her to lie to him right then and there.
But no. A flash of a cold, pale John sends his mind reeling back into unreality, a clutter of possible routes and eventualities. There shouldn't be any space for emotion but it creeps up on him, breathes down his neck uncomfortably, a little reminder that emotion is the reason behind all of this to begin with—why he's using Lestrade's ID to steal a motorbike, speeding off into the night with a woman's arms around his middle. He doesn't notice how steady they are, how she has mirrored his own focus and made it her own. While nervous tremors run up his ribs and down to the tips of his fingers every few moments, she is entirely solid. As though, to her, the thrill of chase is nothing new.
It shouldn't be new to him, either—and yet his body is betraying him.
The fire lights just as they arrive. He glances back for just a fraction of a second, sees the flames alive in her enlarged pupils.
And then he's running. People begin to part like the Red Sea around him but he still pushes them back, if just to gain a little more leverage to push himself forward. His longer legs carry him past Mary, both of them screeching John's name dementedly, unconsciously. They're too close to lose him now. Not like this.
Over the crackle of the fire and the beginning, realizing cries of the crowd he can hear John calling back to him, his voice crackly and whisking itself toward hysteria. He leaps into the bonfire without a second thought.
It takes a moment for the heat to hit him, but he's got into a rhythm by then, tearing apart the pile until he finds skin and cloth and source of John's voice. Mary is right behind him, and together they pull a slightly singed John back out onto the cool earth, as he wheezes and struggles for breath painfully.
"John," Sherlock murmurs finally, placing a hand against the other man's cheek, reassuring himself of the warmth beneath. He's fine, no life threatening injuries, just a bash in the head and smoke inhalation. Nothing they haven't dealt with before.
And that's when it hits him, just as John's eyes are fluttering open more permanently; this is not something new at all. This is John, once again, in the line of fire. John, the victim, because the whole world seems to know that Sherlock will always drop everything and come sprinting after him.
Sherlock leans back on his haunches, head swiveling as he analyzes the crowd. The information floods over him, and yet none of it is out of the ordinary. Whoever is responsible for this has, wisely, cleared out. The tingling in the back of his head has cleared out, too, and he recognizes it better now. It plagued him when John and Sarah Sawyer got snatched by that Chinese gang. When Moriarty strapped that bomb to John's chest. It's a cold, unnerving sweat, and it's distracting.
He directs his eyes back to John, who has shifted onto his side and seems to be attempting to cough up a lung. He wants to tell him he's sorry, for putting him in this situation yet again. For jumping off a building. For every time in the future he's going to be put in peril. He wants to tell him he's sorry for not being able to tell him he's sorry.
But he doesn't.
Because cleverness breeds foresight, he knows this is not the last time he'll be looking down at a bloodied John. John is loyal. John will stay by his side until it kills him.
And this little revelation hurts him more than anything ever should.