A young boy named Luke goes to live with his Grandmother Helga in Norway after the tragic death of his parents. Helga, who shares stories of witches and their child-hating ways, warns Luke to be wary of them. While on vacation in a coastal English hotel, Luke accidentally discovers a grand convention of witches, masquerading as the Royal Society for the Prevention of Cruelty to Children. These witches are led by the terrifying Grand High Witch, who doles out sinister plans to rid the world of children by transforming them into mice.

From this point, Luke and Helga must devise a way to thwart the witches' scheme without falling victim to their dark magic. The courageous pair face numerous challenges and dangers as they navigate through the complex and menacing situation. Using cleverness and bravery, they seek an opportunity to stop the witches from fulfilling their evil mission, all while maintaining secrecy about their discovery.