When Captain Nicaresco tracks down Mike Alexander, a crooked American adventurer, in Parma, Majorca, he tells him that he has one hundred, starving World War II refugees on board his derelict ship, the Chalcis . Nicaresco convinces Mike to help the six men on board who can afford to pay him for onward passage, and Mike charges the men $3,000 each to board his boat, the Black Jack , but fails to persuade a beautiful, penniless woman, Ingrid Dekker, to leave with him. Mike then advises Nicaresco to set the rest of the passengers ashore on the deserted island of Aguilleras. Later, Ingrid wakes up at sea in Nicaresco’s lifeboat, and he tells her that the ship sank and that he could rescue only her after she passed out. He takes Ingrid to Tangier, where Mike spots her in a nightclub and offers to help her, but is again rebuffed. Back in Parma, Mike encounters an old friend, Dr. James Curtis, who is engaged in tropical medicine research and is seeking financial backing for a new laboratory. After Mike gives him the money he made from the refugees, he introduces him to an eccentric millionaire, Emily Birk, and is surprised to discover that she hired Ingrid, in Tangier, to be her traveling companion. The next day, Mike and Ingrid realize that Nicaresco has told them conflicting stories about the fate of the ship, and they rush to Aguilleras to look for possible survivors. On the island, Mike finds the wounded José, who was Nicaresco’s mate, and he tells Mike what really happened on the Chalcis : Nicaresco was lusting for Ingrid and had her brought to his cabin, where he knocked her out. After telling the refugees that they were about to disembark, Nicaresco locked them all in the hold, then flooded it while José put the unconscious Ingrid in the lifeboat. Once Nicaresco was sure that all the refugees had died, and not wanting any witnesses to his appalling deed, he shot José and left with Ingrid. José, who managed to make it to the island, finishes telling Mike his gruesome story and dies. Meanwhile, Ingrid has found the partly submerged wreck in a cove, but Mike decides not to tell her about what he learned from José. She insists that they search the wreck, however, and when she discovers the bodies, accuses Mike of being involved in their deaths by not helping them. When Ingrid returns to the hotel, Emily informs her that she is really a police detective investigating Mike’s smuggling activities and insists that Ingrid use her charms to help trap him and bring Nicaresco to justice. That night, Ingrid tries to seduce Mike and discovers that he is not wholly evil and that he intends to retire from his criminal activities. They begin to fall in love and Ingrid plans to leave with him after his last shipment arrives from Singapore. Two days later, a Spanish naval training schooner sails into the harbor, unwittingly carrying Mike’s contraband. Emily then tells a horrified Ingrid that Mike is smuggling narcotics. Later, Mike throws a party at which Emily reveals to him that she is really a rival smuggler and has hired Nicaresco to steal his drugs. Meanwhile James, who is actually a narcotics inspector tracking the drugs, believes Mike is innocent and being used by Emily, but Ingrid accidentally reveals Mike’s true role to him. Mike locates Nicaresco and, after a long chase, catches him and threatens to drown him unless he reveals where he hid the drugs. Nicaresco takes Mike to the wreck of the Chalcis and knocks him out but Mike recovers, locates the drugs, drowns Nicaresco and empties the drug containers into the sea. On his return, Mike earns Ingrid’s approval when she learns he has destroyed the drugs and they head off together on board the Black Jack . However, James and his Spanish colleague, Inspector Carnero, who has been posing as a suitor of Emily, believe that Mike is escaping with the drugs and soon the Black Jack is under fire from several police launches intent on stopping Mike and Ingrid before they reach the freedom of international waters. Just as Mike tells Ingrid that he loves her, he is shot, then dies in her arms as they cross the international border.