Inconsiderate millionaire John Benson, his spoiled daughter Lydia, philanthropist Oliver North, successful "nature" writer Langdon Crane (author of Back to the Primitive), wealthy idler Robert Curtis, and Curtis's valet, Parkes, are among the passengers on an ocean liner that is sunk by a German submarine. Carried away by the currents to a tropical island, the castaways must not only survive, but avoid the German submariners camped there. They endure hardships which bring out their true natures. Benson becomes kind and considerate underneath his gruff exterior; North exhibits a meanness and smallness; Crane, it turns out, is not the rugged survivalist he portrayed in his book, but a coward and slacker; and Curtis develops into a dynamo of activity who, with Lydia, manages to canoe to another island forty miles away, where an American wireless operator contacts a nearby U.S. battleship, which shells and destroys the German camp and rescues the Americans. Curtis's strength and consideration prompt Lydia to fall in love with him. As the rescue ship carries them away from the island, the two sweethearts hold hands.