Lt. Comdr. Ericson is made captain of a British corvette, a small escort vessel used to guide and protect a convoy traveling through the Atlantic. Ericson had his confidence severely shaken during his last command, in which he lost his ship HMS Compass Rose and most of its men following an attack by a German U-boat. With handful of men on a raft Ericson barely survived. This time on board the frigate Saltash Castle, he leads a new and largely inexperienced officers and men just out of training. The winter seas make life miserable enough, but the men must also harden themselves to rescuing survivors of U-Boat attacks, while seldom able to strike back. Once again Ericson is thrown into a life-and-death dilemma that forces him to choose between destroying an enemy ship and sparing the lives of his own men.