In a deep bowl between the Heidelberg hills lies Lake Vanuka. It has neither inflow nor outlet, and its depth has never been measured. Geologists say that when the Great Ice Age melted, its waters filled an incredibly deep depression here. That was fifty thousand years ago. Beneath the calm surface of the lake lies another world inhabited by little people. These people live forever and don’t know what diseases and death are. In the past, they owned the Earth alone, and now they want to take it back. The archaeologist Hugh Lambert finds himself drawn into the lake’s tranquil depths and learns about a sinister plan to conquer the Upper World.