John keeps his collection of hearts piled up in a corner of his room, collecting dust.
They don't look like hearts, of course. They can look like anything, like a stuffed bear that John won for his first girlfriend at a carnival, like the theme music of a show he used to watch every Saturday with his sister, even if they were fighting at the time, like a bottle of perfume or a favourite drink or a particular scented lip balm - but every one of them is someone's heart.
He studies them, tries to form a picture of their previous owners. He stops because the dust, the dents, the careless way they are tossed aside makes something twist low in his gut.
"I'm not going to join your collection," he tells John at breakfast, half-suspecting himself of lying.
John looks at him, blinks disingenuously. "That's what you've been so worried about? They're just hearts, Sherlock. People give them away all the time."
"Not me," Sherlock says.
"Not you," John agrees. "That's okay. There's three ways to gain someone's heart. One of them is bound to work."
"Oh?" Sherlock says (touches his chest to make sure his is still there).
"Mm," John says. "You can lose a heart -"
"Careless," Sherlock says, tries to make his words light like air.
"Not really," John says, shrugging. "It's hard to keep hold of, you know, it slips through your fingers when you least expect it and falls into someone else's hands. That's the first way: someone loses their heart to you."
"Not me," Sherlock repeats. "I would never be so careless."
"Right," John says, nodding. "I'm never quite sure what to do with that sort, anyway. I mean, I get how hard it is to hold on to, but still, anybody could have caught it, in the right time, the right place. It doesn't mean anything. What if I didn't even want it?"
"You should give it back, then."
"It doesn't work like that," John says patiently.
"It just doesn't," John says, a statement of fact that everyone should know - grass is green, sky is blue, Bank Holidays are wet and miserable, you can't give someone their heart back. "You've got to take your heart back. That's the way it works." He spreads jam very evenly on his toast as he thinks, says lowly, "It's... difficult, and most people leave a little of their heart behind even when they do."
"I don't understand," Sherlock says.
"Didn't think you would," John says. "I bet you'd erase every sign that anyone else had ever held yours."
Sherlock's hand curls against his chest, tight against his sternum, heartbeat steady against his fingers.
"The second way," John says, "is to give your heart to someone. Always fraught with risk, that. Even worse than just losing it, because you've done it deliberately."
His eyes linger on something behind Sherlock, but when Sherlock turns and looks, all he sees is John's abandoned cane, leaning against the wall.
"And third... third - you have your heart stolen."
"And are you good at stealing hearts?" Sherlock says, though he's pretty sure he already knows the answer.
"Very good," John responds promptly, without a trace of smugness. "It's okay, though, I won't steal yours."
"Maybe you won't mean to," Sherlock says dubiously, meaning but you will all the same.
John shakes his head. "No. When you want someone's heart, I mean, really, truly want it, you want them to give it to you, you know, as part of a proper exchange."
Sherlock's hand stays pressed against his chest. For all John's talk about how he wouldn't steal Sherlock's, he's not sure John wouldn't take his heart accidentally, just being John. "In exchange for what."
John blinks at him, eyes wide with surprise. "Your own, of course."
He looks at his cane again, then back at Sherlock's face. "It's okay," he says gently. "I mean, you've already got mine. I can wait."