The Lost Princess of Oz

In L. Frank Baum's Lost Princess of Oz (1917), Dorothy awakens one morning to discover that Princess Ozma has disappeared, along with several magic items belonging to Glinda and the Wizard. A search party comprising Dorothy, the Wizard, Betsy Bobbin, Trot and Button-Bright is formed and the friends set off for the land of the Winkies. But who is behind the mysterious disappearances? The eleventh in the Oz books series, its plot was inspired by a letter from a young fan.