During World War II in England, Charlie, Carrie, and Paul Rawlins are sent to live with Miss Eglantine Price, who turns out to be an apprentice witch. Charlie blackmails her that if he is to keep her practices secret, she must give him something, so she takes a bedknob from her late father's brass bed and places the "famous magic travelling spell" on it, and only Paul can activate it. Their first journey is to a street in London, where they meet Professor Emelius Browne, the former headmaster of Miss Price's witchcraft-training correspondence-school. She tells him of a plan to find the magic words for a spell known as "Substitutiary Locomotion", which brings inanimate objects to life. This spell will be her work for the war effort.