Perry Rhodan has discovered a huge space ship, an ark in space, carrying a population of humans who set out on their journey 55,000 years ago, from Earth - Lemurians, the legendary forefathers of mankind.

The alien Icho Tolot, one of Perry Rhodan's closest friends, is hurled back in time into the final years of the onslaught of the Beasts - his own ancestors. He becomes a witness to the devastation brought about by the Beasts on the Lemurians and meets the scientist Levian Parron. Unwittingly he inspires Parron to create the arks - and to undo the onslaught of the Beasts ...