The summary is: 1) The story is set in Norway and England in the 1950s and follows a young boy and his grandmother. 2) The grandmother tells the boy stories about witches and how to identify them. 3) The climax occurs when the boy attends a witches' meeting and is turned into a mouse by their chocolate. 4) In the end, the boy and grandmother turn the tables on the witches by using the witches' own magic to turn them into mice.