Young Luke and his parents visit his grandmother Helga in Norway during vacation, and she tells stories of evil witches, such as how her best childhood friend was kidnapped by a witch. After Luke's parents die in a car accident, Helga becomes his guardian and they move to England. One day a woman approaches Luke, but he recognizes that she's a witch. When Helga falls ill and her doctor diagnoses diabetes, she and Luke travel to a seaside hotel, where Luke befriends plump Bruno Jenkins and has problems with hotel manager Mr. Stringer over his pet white mice. Meanwhile, a group of women from the Royal Society for the Prevention of Cruelty to Children arrive for a convention, led by Miss Eva Ernst. But soon Luke learns that Eva is indeed the Grand High Witch and their convention is to distribute a magic potion to turn boys in England into mice. When the Grand High Witch sees Luke, she turns him into a mouse. What will he do?—Claudio Carvalho, Rio de Janeiro, Brazil