Every evening, Mira sat on the underpass steps and played the same eleven notes. She never named the tune. It just showed up in her fingers one cold winter and stayed. Coins dropped into her open case while she played. But tonight a padded envelope was already waiting on the step. The address was written in her own slanted handwriting, even though she had never mailed a thing in her life.

Mira tore the envelope open. Inside was a single folded page covered in music notes, with one line written at the top: 'Play it backward.' The notes were her eleven, but flipped end to end. Her hands went cold. She set the page on her knee and picked up her instrument.

She played the eleven notes backward. The sound came out wrong and right at the same time. The streetlights flickered. For one second Mira saw herself sitting on the steps from above, as if she were floating up near the ceiling. Then she snapped back, breathing hard.

When the world steadied, a man was sitting beside her on the step. He looked tired and kind, a little like her father. 'You felt that,' he said. 'Good. The song is a key, Mira. You've been winding it up for months without knowing.' He pressed a small brass disc into her hand, and at once the eleven notes rang out with no instrument. The underpass folded away and she stood in a quiet white room full of doors.

Mira chose the nearest door and stepped through. She landed back on the underpass steps, on the very first winter night the tune arrived. A younger version of her sat there, lost and cold. Mira knelt, took the girl's hands, and gently taught her the eleven notes. The loop was finally closed, and she felt at peace.