Nobody used locker 247. It sat at the very end of the east wing corridor, past the point where the fluorescent lights started to flicker and the floor tiles changed from beige to a darker, older brown.

Mira walked past it every day on her way to AP Chemistry. She'd never given it a second thought until the morning she heard music coming from inside. Not the tinny, distant kind that leaks from someone's earbuds — this was full and warm, like a cello being played in a concert hall.

She pressed her ear against the cool metal. The music swelled and faded, swelled and faded, as if the locker itself were breathing.

'You hear it too?' A voice behind her made Mira jump. It was Dev from her English class, holding his books against his chest like a shield. 'I've been hearing it for weeks.'

Together, they stood in the empty hallway and listened. And for reasons neither of them could explain, it felt like the most important thing they'd ever done.