Handy Mandy in Oz by Ruth Plumly Thompson is an adventure following Mandy, a resourceful girl with seven arms, as she journeys through the magical land of Oz. Armed with her unique abilities, she aids King Kerr of Keretaria in reclaiming his throne from an evil usurper, encountering strange creatures and new friends along the way. The story highlights themes of ingenuity, friendship, and the triumph of good over evil, all set against the colorful backdrop of Oz.