In Vichy France, fishing boat captain Harry (Humphrey Bogart) avoids getting involved in politics, refusing to smuggle French Resistance fighters into Martinique. But when a Resistance client is shot before he can pay, Harry agrees to help hotel owner Gerard (Marcel Dalio) smuggle two fighters to the island. Harry is further swayed by Slim (Lauren Bacall), a wandering American girl, and when the police take his friend Eddie (Walter Brennan) hostage, he is forced to fight for the Resistance.