Pop has just passed one of her witch exams, but gets into a heated argument with Doremi because Hana followed her into the Witch World. Initially unbeknownst to everyone, the flower Pop brought home from the Witch World is really the Witch Queen Heart, the Queen's favorite flower, which grants any wish it hears regardless of any possible dangers until it begins to bear seeds. One of the wishes it had granted involves turning Doremi into a mouse, unknowingly made by Pop over her anger towards Doremi. While Pop goes to search for her sister, the other girls track down the runaway flower before it starts to reproduce. (thetvdb.com)