So this is the end of the world, he thinks to himself. This is what happens when a light blinks out and all the fibers inside it vanish as well. It's far more silent than he thought. It seems that an entire world, a whole galaxy, should make more noise than this. There should be some final scream, some huge rending of the veil, but no – there's nothing. Complete silence. Planet Earth is being ripped apart by solar flares, and nothing, nothing, nothing will remain.
He wanted to tell John, to warn him of the impending peril so he could put his affairs in order, but what was the point? Why bother, when all the affairs he could manage would disappear alongside him. Forgiveness doesn't matter, love doesn't matter, nothing matters when everything ends all at once. Only survivor's guilt compels the ordinary rituals of repentance and acceptance. The promise of a future without the dead is what drives us to reach out to others in our last hours. But when there will be nothing beyond the end, there is no reason to fix what is broken.
So he lets the man sleep, curled up safe in his bed like a kitten in its nest of blankets. John's room has the best view of the night sky, and he steals up, minding the creaking floorboards, and stands at the window. A shaft of moonlight lands on the doctor's face, serene in dreamland. He wonders idly what John dreams of: if he ever features in his flatmate's dreams, or if he uses that time to get away from him, to live out a life where he's not dodging bullets on a weekly basis. Surely he is not dreaming of the Apocalypse. No, Sherlock faces that terror alone.
The scientists have done all they can to hide this from the public; why worry everyone? The end is inevitable, unavoidable, and so to protect societies, to let the world go out in peace, they have repressed this information. Good for them. He would rather remember London this way: peaceful and smooth under the brightening moonlight. A shining city of commerce, of culture and history. A microcosm of the best and worst of British society, and god, he mourns it already. To see this all wiped away, everything he has ever loved and fought for, and to know – to know that it's over – it breaks his heart. Because no one will remember Planet Earth after they are gone. No one is watching them. No rescue will come. This is the end, and he must watch it play out, every agonizing second, alone.
John rustles in his sleep, moans softly. He is suffering a bad dream. Sherlock checks his watch – 5 minutes to go. There isn't time to explain, and he doesn't want to watch it, not like this. He breaks every rule he has in his body, and he pads over to the bed, slipping in beside his best friend and wrapping his arms around the doctor's stout frame.
"Sherlock …? What –"
"Shhhh." He tries his best to sound gentle, but the words come out choked, and the world is all wrong, and he can't bear it.
"Go back to sleep, John."
The man slips back into his dreams easily, his breathing soft and measured. Sherlock burrows his face into the crook of John's neck, which smells so strongly of his cologne, his favorite brand of soap and a bit of musky sweat. This will be the last thing he ever smells in this world. A tear slips down his cheek.