In the present day, Time Agents Ross and Gordon come with settlers to the water-dominated planet, Hawaika, to search remains of the alien Baldies from the distant past. Local intelligent dolphins assist them. While investigating, a time gate fails, destroying itself and stranding them widely in the unknown past. The native dolphins and humans can communicate, and Ross learns Gordon is hostage in a castle through a native, Loketh. Ross and Loketh are captured by seafaring Rovers, then join them.