Janetta had a magnet and Marvin wanted it. Because Janetta's imagination was much stronger than any magnet, Marvin, a very shrewd bully, had a power over her that he sensed and seized, by the suggestion of mysterious powers. During the length of time that the two struggle -- Marvin for the magnet and the upper hand (which he always needed) and Janetta for her property and her strength of mind over the vivid fears that Marvin could induce -- her mother is away, her older sister has almost forgotten what a nightmare small girls can create for themselves and her comfortable father can't even begin to understand. Girls in this age group will be able to empathize, knowing as they do the attractive and repellent reactions that accompany the process of investing a small fear with the ability to blow up and run away with reality. Marvin is hoist by his own petard at the end of a very satisfying book. The perception that Mrs. Lattimore has brought to her other well-known and outstanding books is apparent here.