My name is Walter. I’m sixty-six, and I have kept the floors of Lincoln Middle School for twenty years. The old grand piano in the assembly hall has stood under a dust sheet since the music programme was cut.

Every night after the last bell, when the corridors are empty, I lift the sheet, wipe the keys and play for ten minutes. Nobody knows. I never planned for anyone to.

Tonight two students had stayed late for detention and were watching me through the gap in the hall doors. A boy in the back row was tapping the rhythm on his knee. A girl in a blue hoodie had tears in her eyes.

Then I heard footsteps. Principal Hale stood in the doorway in his navy suit, his briefcase in his hand, his mouth slightly open. I stopped playing at once, but he said quietly, ‘Please don’t.’

‘Sir, I’m sorry,’ I said. ‘I only wanted to keep the strings in tune.’

‘Where did you learn to play that?’ he asked.

I told him the truth. I had studied at a conservatory in Prague, long ago, in another life. A war ended my career and my country, and I came here with one suitcase and a broom.

He walked to the piano and ran his hand across the lid. ‘Our budget for the music programme was cut three years ago,’ he said. ‘The board voted it out. I signed the order.’

‘I know, sir,’ I said. ‘It was not your fault.’

‘It was,’ he said. ‘And I’ve regretted it every day.’

The two students had come into the hall without a sound. ‘Can you teach us?’ the boy asked.

Principal Hale looked at me, then at the children, then at the piano. ‘Walter,’ he said, ‘would you take the position? Not as a janitor. As our music teacher.’

I thought I had misheard him. Then the girl in the blue hoodie sat down beside me on the bench and put her small hands on the keys.

The music programme reopened in January. Forty-one students signed up. On the opening night, the whole school stood when I walked in, and the hall was filled with the sound of a piano that had waited three years.