Based on a short story by John Steinbeck, Lifeboat takes place entirely on a boat adrift in the North Atlantic. After their Allied freighter is sunk by a German U-boat, a diverse group of individuals make their way onto a lifeboat. Later, the castaways rescue a man adrift at sea, only to discover that he is the very German U-boat captain who sunk their vessel. Choosing to keep him aboard as a gesture of humanity and for the sake of his seafaring skills proves to be a fateful decision for the survivors when they discover the German captain's true motives.