In the summer of 1940 American Harry Morgan lives in Martinique, a French colony in the Caribbean. He takes tourists out sports fishing and tries his best to mind his own business, especially when it comes to politics as the Nazis have just invaded France. Unable to collect from a client who is killed by a stray bullet and in need of cash, Morgan agrees to smuggle a Free French leader onto the island. With the help of a new friend, Marie 'Slim' Browning and his pal Eddie, he tries to stay one step ahead of the local secret police. Morgan quickly realizes he needs to get out of Martinique but complications arise forcing him to take sides in the fight after all.