Inhabitants of Oz are noticing unusual signs of aging.
Omby Amby finds a white hair in his luxurious green beard, and common citizens confront wrinkles and back problems. Ozma and her advisers realize that the magic anti-aging spell, which has prevailed in Oz throughout her reign, has now stopped working. In their attempt to figure out why, Ozma and
Glinda consult the
Great Book of Records, but find cryptic references to the "Man Who Lives Backwards." (This person is actually living in Glinda's palace at the moment; but since he lives backwards, he is a baby in the present time, and cannot explain himself to them.) In trying to puzzle out the problem, Ozma and Glinda confront a Parrot-Ox, a large magic creature, half parrot and half ox. They learn that these creatures, normally invisible, are amazingly common; they co-exist with us in our everyday lives. A Parrot-Ox is "capable of doing nothing at all, unless it is impossible." This particular Parrot-Ox calls himself Tempus. To resolve the mystery of the aging of Oz, Ozma rides Tempus back in time, to meet her predecessor King Oz in the forest surrounding the Forbidden Fountain. She encounters a curious person called Dr. Majestico, and she accidentally changes the past so that Oz becomes an evil place, ruled by a tyrannical Wizard from an Obsidian City, a negative-image of her own Emerald City. She must deal with altered versions of her familiar friends: the beautiful Glinda is old and worn, while the
Tin Woodman is a human and very malevolent headsman, Nick Chopper. In her efforts to remedy the situation, Ozma takes more and more trips into the past; the woods around the Forbidden Fountain are soon filled with Ozmas from different times. Ozma must confront Tip, her own earlier male self, and take a journey to Absurd City to find the Man Who Lives Backwards; she must face mind-boggling confusions, and numerous Parrot-Oxes, before she can restore the familiar world she knows and loves. ==Ozian allusions==