The tense situation in Nazi occupied France also hits the French colony Martinique in the Caribbean. In its capital Fort de France an American sea captain, Harry Morgan, has some trouble with the local authorities, who is all the time spying on possible collaborators of the resistance movement. But Harry Morgan is a recluse, who doesn't want to be involved in anything. He keeps all persons at a distance, except the alcoholic sailor Eddie, who he cares for. A young woman, Marie Browning, age 22, moves into Hotel Marquis in the room opposite his. She immediately captures his interest, and she is also affected by him. Morgan thinks this isn't a proper milieu for a young woman, and wants to help her get back home. To be able to pay her flight ticket, he contacts the resistance movement, saying he accepts transporting two persons from Anguilla to Martinique with his fishing boat in the night, if he is well paid. During the operation they are spotted by a patrol boat, but Morgan extinguishes their lantern by a gunshot, and slips away with his boat. Next morning Sûreté Nationale, the French equivalent to Gestapo, suspects Morgan for being the one who brought two resistance fighters to Martinique and tries to press him to reveal their hiding place.