During World War II Hans Kyle, a German deserter is living in India under the name of Robert Crain. The British Intelligence officer Colonel Statter blackmails him to impersonate an SS-officer in order to get aboard a German blockade runner that is conveying a valuable rubber cargo from the Orient. Crain's assignment is to save the rubber by finding a way to deactivate the explosives that the ship's captain would use to destroy the ship if captured by the enemy. Crain finds his way aboard the ship, but the ship's commander Captain Mueller, skeptical of the Nazis, refuses to let Crain out of his sight. When survivors of a sunken vessel board the ship, and Crain realizes that his identity may be exposed by two rescued German submarine officers, he incites Mueller's officers and the new arrivals to mutiny before his true identity is revealed.