 Ship engineer Jim Taggert (John Litel) is rescued from a torpedoed tramp steamer by Joe Morgan (Alan Baxter), an American gangster that found New York too hot for him, and has become a fisherman operating from an out-of-the-way island off of the coast of South America. Morgan makes his headquarters at the Halfway House run by the parents of Maria Styx (Fifi D Orsay) as a bar and dance resort catering to the planters and traders of the island. Taggert finds himself practically a prisoner along with a group of American girls acting as entertainers at the resort. Taggert shadows Morgan in his activities in a remote cove and finds that Morgan is supplying German U-boat commanders with torpedoes, but does not know that Morgan has rigged the torpedoes with clock devices that explode when at sea and sinks the U-boats.