In 1906 a detachment from the U.S. Signal Corps is attacked by three Tu-nel. The Tu-nel are descended from the therapsids, mammal-like reptiles that evolved in the Triassic Period--before the dinosaurs. They co-existed with the dinosaurs of the Jurassic and Cretaceous Periods. During the 135 million years of their existence, they have undergone major evolutionary changes. These helped them survive the mass extinctions of the dinosaurs and, much later, the giant mammals

The scene shifts to Hampton Roads, Virginia. Teddy Roosevelt is launching his Atlantic Fleet on a world cruise. It is an audacious enterprise, mainly because of the political tensions between the United States and Japan. The oldest ship in the Fleet is the Florida, commanded by Captain Oates. His vessel is constantly in the "Observation Ward" because of poor performance, a position that does not improve after the Fleet sets sail for South America. It is his ship that will ultimately confront the Tu-nel off Midway Island.