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.