Prospecting in the Wyoming badlands, Patricia Savage spies a man swimming in circles¿high in a cloudless sky! After he falls to his death, the dead swimmer is discovered soaked to the skin. Who is he? How did he manage to swim through thin air? These are the questions Pat sets out to answer when her cousin, the famous scientist-adventurer Doc Savage, diagnoses her account as a hallucination caused by altitude sickness. But when the bronze-skinned girl vanishes, the Man of Bronze is forced to take action.From the Bighorn Mountains to Devil¿s Tower, Doc Savage and his mighty crew race against time to avert an impending tragedy created by a nebulous devil in human form who calls himself Mr. Calamity.