When three adventurers, Bastin, Bickley, and Arbuthnot, are marooned on a South Sea island, they discover an ancient crystal sepulchre. Inside are two Atlanteans who have been in a state of suspended animation for 250,000 years! One of the awakened sleepers, Lord Oro, is the last of the Sons of Wisdom, a superior race who'd relied on their advanced technology to subjugate the planet's lesser peoples. The other Atlantean is Oro's daughter, Yva, heiress the title of Queen of the Earth. Unimpressed with the state of the world in the early 20th century, Oro sets out to do what he's apparently done once before: use a colossal gyroscope to drown the planet, and restart the course of human history.