The boy's diary describes losing his parents in a car accident and living with his grandmother. His grandmother tells him scary stories about witches and teaches him to identify them. While building a treehouse with his friend, the boy sees a woman he believes is a witch staring at him. He hides from her in the tree and tells his grandmother. Later, the boy overhears a group of witches planning to kill all children with a formula. At the end, the boy and his grandmother's plan works to transform all the witches into mice.