The film is based on the children's novel of the same name by Roald Dahl (the original author of "Charlie and the Chocolate Factory"). It is partly set in Norway and partly in the UK. It tells the story of a 7-year-old boy who lives with his grandmother. There are evil witches in this world. One time he encounters the witches and is turned into a mouse. He must try his best to stop them from destroying the world.