The main character of the story is a little boy named Luke, whose grandmother often tells him about children’s greatest enemies: evil witches. After the tragic death of his parents, his grandmother takes him to England, where the boy encounters his first witch. Fortunately, thanks to his grandmother, he knows exactly how to recognize such a witch and how to defend himself against her tricks. His best friends are two white mice, William and Anna, whom he received as a birthday gift. He takes them with him to the seaside, where he accompanies his sick grandmother. At the same time, members of the Royal Society for the Prevention of Cruelty to Children—who are actually witches—arrive at the luxurious hotel. The society’s president is Miss Ernst, who enjoys talking with children but must turn her face away because the pure and truthful child smells unbearably bad to her. Luke accidentally witnesses a gathering of all the English witches and overhears their plan to poison all the children. The witches are to become confectioners and add a potion to the sweets that will turn the children into mice. The chubby Bruno Jenkins is to serve as the guinea pig. But Luke doesn’t escape the witches’ attention either, and in the form of a mouse, he flees the hall together with Bruno, William, and Anna. Together with his grandmother, he then tries to thwart the witches’ evil plans.