During World War I, a German U-boat sinks a British ship and takes the survivors on board. After it takes a wrong turn, the submarine takes them to the unknown land of Caprona, where they find dinosaurs and neanderthals.

Major Ben McBride organizes a mission to the Antarctic wastes to search for his friend who has been missing in the region for several years. McBride's party find themselves in a world populated by primitive warriors and terrifying prehistoric creatures, all of whom they must evade in order to get back safely