A boy called Theo was supposed to clean the paintbrushes after art club — really clean them, in warm water until the colour ran clear. It was the boring end-of-session job nobody enjoyed. This time he was in a rush to get to the playground where his friends were waiting. So he gave the brushes a quick swish, shook them, and stood them up looking clean enough. From the top they looked fine. Deeper down, the paint was still in there, drying hard. Next week the brushes were stiff and ruined, and the teacher asked who'd cleaned them last. Theo remembers it was him. He also remembers thinking, at the time, that nobody would ever check that far down.