The tide crept in on gnarled fingers. Scabs of foam clotted the shore, raking the sand and creeping up, up, up to whisper under the little girl’s window.

‘Come out and play, pretty child,’ the mermaids sang. ‘We’ll give you a necklace of pearls.’

‘No,’ said the little girl. ‘I must stay in bed like a good child.’

‘The pearls gleam like shark’s teeth,’ the mermaids chanted. ‘Worms crept between the oyster’s lips and anguished its flesh till it wept solid shimmer. We’ll hang its tears around yo...