Prompt: As soon as he can after the Fall, Sherlock sneaks back into Baker Street and hides his heart somewhere in the flat. John either doesn't find it or only finds it after some time has passed, so he doesn't realize it's Sherlock's, but the sound of it beating comforts him when nothing else can.
John keeps his heart in an old tin meant for keeping tea, small, rusting and inconspicuous.
It's unexpectedly small, John's heart, if you're not bothering to observe, as most people wouldn't. Most people looking at John's heart, small enough to fit into a child's palm, would think him detached, indifferent to others, untouched by any of the emotions that make a heart grow. John would never let his heart be seen up close to prove them wrong.
Sherlock studies the grooves, the scars, the evidence of countless bites and knives taken to it, of the many times John has divided his heart into pieces and given them away. What remains is pure John, and its steady unrelenting beat is so much stronger than would be expected from something so shrunken and small.
It's not pretty. More scar than heart, really, although it's healing, slowly, as all hearts do. Despite that, Sherlock knows that if he touched it, it would be soft under his fingertips – proof that while John may have learned to hide his heart he has never learned how to stop giving it away to anyone in need, anyone who asks, anyone who wants it and plenty who don't, who have no idea what a gift it is.
He doesn't touch it.
The tin no longer smells of tea. John's heart is torn open as he stands to attention at Sherlock's funeral, its steady beat turned into the reedy, exhausted whisper of blood endlessly expelled.
Sherlock's own heart – as anatomically correct as John's, though marked with the intricate web of a London road map rather than veins – gives a terrible shuddering lurch in his pocket.
It is larger than John's, barely touched, and won't fit inside the tin to rest next the one that needs it most. It would have, before he and John met – but then, he would not have wanted to put his heart in this tin before they met.
Sherlock wants very badly to touch John's heart, to press the gaping edges together and try to seal them shut with his fingers, anything to stop looking at the raw open wound of it.
we did this, he thinks he hears his own heart say, his sleek untouched heart, smooth as glass and twice as hard.
He puts the lid back on the tin, leaves John's heart alone in the dark, swimming in its own blood and hurt. He can't take it with him.
He thinks he might be starting to panic. Funerals don't last forever.
somewhere he can hear me, counsels his heart. He imagines it has a very low voice, hoarse and unused, and he gives a soft, desperate huff of laughter because he's never heard his own heart before.
stupid, says his heart. I'm not here for you. I never was.
When John finds Sherlock's heart, Sherlock feels it.
He feels John's fingers tracing featherlight across the network of streets and alleys and roads and lanes, every one of them neatly labelled and named.
The name of the heart's owner, carved at the centre of a great cluster of roads, is visible only when the light hits it just right, and Sherlock can't feel John's touch there.
When he gets home he'll point it out to John. He'll take his hand and guide his finger across the tiny letters and say 'look, you are here' and John will choke back laughter at the terrible pun.
When he goes home.
In the meantime, his heart sings.