After a luxury liner sinks, the officer in charge of an over-crowded lifeboat has to decide who can stay on board.

In the late 1800's, the luxury cruise liner the SS Crescent Star strikes a discarded land mine in the South Atlantic and sinks in the ensuing explosion. Of the ship's 1,156 passengers, only twenty- seven survive. Among them is Executive Officer Alec Holmes, who clings to the flotsam of the ruined vessel. When Alec sees ship's nurse Julie White, with whom he is in love, foundering in the water, he swims out to save her. From a lifeboat in the distance, Will McKinley, one of the ship's officers, beckons to Alec and Julie to join them. The boat, built to hold nine passengers, soon is overburdened by the twenty-seven survivors that have sought refuge there. Once Alec reaches the boat, the ship's fatally injured captain, Paul Darrow, passes his command and his cherished ring to Alec, admonishing him to "save as many as he can." After Darrow dies, Alec dons the captain's jacket, then orders his body cast over the side. Alec's first crisis of command arises when Aubrey Clark, one of the passengers, begs to keep his beloved dog aboard. After the blustery Maj. Gen. Barrington demands that the dog be sacrificed, Alec brandishes his revolver and threatens to charge the major with mutiny if he refuses to follow orders. Alec then declares that the dog will stay aboard to serve as food if necessary. When Alec asks Jill to examine the passengers for injuries, she reports that Frank Kelly, the ship's engineer, has been riddled with parts from the engine explosion. Mrs. Kilgore, the mother of little Peter, is suffering from broken ribs, and Mrs. Ruth Spencer has a battered arm that will have to be amputated. With only one gallon of water aboard, Alec allows the survivors only two sips a day and warns that anyone countermanding his orders will be thrown overboard. Alec's hopes that a nearby cruiser is steaming to their rescue are dashed when he learns that "Sparks" Clary, the ship's radio operator, was unable to send out a distress signal because the ship's transmitter had been smashed in the explosion. With no other alternatives, Alec calculates that the closest land is in Africa, 1,500 miles away. To alleviate the overload, Alec orders the men to take shifts floating in the water beside the boat. Sarcastically addressing Alec as "brave captain", socialite Edith Middleton insists on taking her own turn in the sea. As Mrs. Kilgore begs for a drink of water, the dying Kelly warns Alec that unless he disposes of the "useless" passengers, all will die. As a storm approaches, Kelly stands up and proclaims that he is dead, as are Mrs. Spencer and Mrs. Kilgore. After declaring that Alec must put twelve people over the side, Kelly leaps to his death. When the winds begin to rage, Alec startles the survivors by announcing that the weak must go and orders McKinley, his second-in-command, to toss Mrs. Spencer over the side. Shocked by Alec's heartlessness, McKinley goes overboard with her. Next, Alec orders Mrs. Kilgore and her husband George into the water. When George insist that their young son Peter join them, Michael Faroni, one of the passengers, promises to take care of the boy, who then watches as his parents are cast away to certain death. After Alec orders Aubrey into the water, his dog leaps in after him. The elderly Mrs. Dorothy Knudsen meets her death with dignity when she is commanded to go overboard. Julie watches in horror and disbelief as Alec pronounces the death sentences, one by one. As Edith recites the roll call of death, Faroni pulls out a knife and orders Alec to turn back and save the others. Alec's revolver is out of bullets, so he seizes a flare gun and shoots Faroni. Before dying, Faroni hurls his knife into Alec's shoulder. As the storm hits with gale force winds, Alec rallies the survivors to keep rowing. When the storm finally wanes, the survivors are amazed that they are still alive. Although the others thank Alec for saving their lives, Jill warns that he will live in shame for his actions. Believing that he is dying, Alec passes his command and ring to Clary, then jettisons himself overboard. After the others pull him back into the boat, a ship's horn is heard in the distance and they fire a flare to signal the vessel. As the ship steams toward them, every survivor literally turns his back on Alec, except for Edith, who insists that he made the right decision. After thanking his crew for their courage and help, Alec instructs them to row toward the ship. Upon reaching their rescuers, Clary turns and hands the ring back to Alec. Later, after facing trial for murder, Alec is convicted, but sentenced to six months in prison due to extenuating circumstances.