Mark Sheldon, a secret service operative, is assigned to investigate a modern slave racket that is hiring paroled convicts into hard labor on an obscure island in the Pacific. When Sheldon's partner is murdered just as he is about to reveal that Stephen Danel is the head of the racketeers, the agent goes undercover to solve the case himself. Suave and relentless, Danel works the men to death, constantly recruiting new workers at the prison gate. One of these new workers is Sheldon, who has framed himself for the murder of a fellow operative and is pretending to be an ex-con. On the island, Sheldon remains silent as he witnesses Danel's cruelty to his wife Lorraine and cook Siggy. Lorraine senses that her only hope lies in the defiant Sheldon, to whom she is attracted. Sheldon escapes his confinement long enough to instruct Lorraine to bring him Danel's keys, but soon after he is recaptured by Cort, the brutal guard captain. Playing on Cort's greed, Sheldon offers to split Danel's fortune with him, and Cort allows Sheldon to return and incite the prisoners to revolt. As Lorraine delivers the key to Sheldon, they are surprised by Danel and his guards. Sheldon's plans are further disrupted when the prisoners revolt and Cort seizes leadership from Sheldon and announces that he will take care of Lorraine. Sheldon runs to Danel's house to warn Lorraine, but soon finds himself facing Danel's gun. As Danel pauses during Sheldon's execution to taunt Lorriane, Siggy hurls a knife into his back. After Sheldon subdues the remaining guard and enslaved workers, his mission is accomplished and he and Lorraine fly home.