Detective Jackson is taking Frank Howard from South America to New York to face a murder charge when their ship is wrecked. All escape the wreck but Jackson, Howard, and wealthy Dorothy Fairfax. The wreck drifts into the Sargasso Sea, where a fleet of derelicts is inhabited by some 50 people headed by Peter Forbes. To save Dorothy from marriage to Forbes, Frank defeats the ex--sea captain in a fight, then marries her himself, though in name only. Frank calls on his past experience to equip a submarine and make an escape. He wins Dorothy's love and proves his innocence.