In a whirl of rainy weather, a strange woman appears on Theo and Dodie's doorstep making Theo very uneasy. His mother and little sister do not seem at all alarmed by her. Dodie loves Mrs Scarum's stories and her wild dancing. But Theo suspects there might be trouble afoot, not helped by the fact that his father, usually so reliable, has failed to return home. And when Theo is told that you can tell a witch because, if she cries, her tears will turn to crystal, he knows that Mrs Scarum is a witch. Or perhaps this time, tears will make things better?