The sailing vessel Cannibal has a leaking hull. The captain (Rock Hudson) reluctantly changes course for Honolulu, where one passenger (Cyd Charisse) is wanted by the law. The water rising, everyone struggles against nature to survive.
Having seen better days, the sailing vessel Cannibal sets out for Mexico from the south Pacific with a leaking hull. The captain (Rock Hudson) is haunted by a tragedy that happened on another ship under his command. Believing the vessel to not be seaworthy, the crew pleads to change course for Honolulu. Being wanted there in connection with a man's death, a passenger (Cyd Charisse) wants to avoid Honolulu. As the water rises in bilge, the passengers and crew struggle against nature to survive.
In the South Pacific, against the advice of the shipping clerk, Mrs. Charlotte King books passage on the first possible ship leaving port, a ramshackle brigantine named the Cannibal that is headed to Mexico. Onboard, Captain David Bell and his first mate, Ramsay, welcome their other passengers, theatrical manager Harry Hutton and his singer, Ethel Peacock; missionary Reverend Butterfield; and emigrants Feodor and Ida Morris. The passengers, who will be together for several months, are polite to one another at dinner, during which Charlotte questions the taciturn David but receives few answers about his past or the ship. After dinner, Ramsay points out the ship's many leaks to David and insists that they pump out the water filling the bilge, but David refuses to pump until the passengers are asleep, hoping to avoid worrying them. Later, Ramsay, who believes he recognizes Charlotte, approaches her amorously, but she rebuffs him. In the middle of the night, Harry hears the bilges being pumped and confronts David, who responds gruffly but later suffers the painful memory of the sinking of a ship under his command, in which thirty-seven people died. Although at the time of the sinking, David had heroically remained awake for five days desperately trying to steer the ship through a storm, a court found him guilty of negligence, and revoked his license. David now finds his only solace in whiskey, but tries to avoid its succor. In the morning, a worn mast tears loose, and David risks his life to repair it. Impressed, Charlotte visits him in his cabin, and wins him over by easily charming his dog, Anchor. After David leaves to go to work, Charlotte reads a journal entry in which he has written how much he needs this voyage to succeed. The ship stops at the Marquesas islands, where they are joined by Oliver Randall Wiggins, a British playboy who immediately taunts Butterfield about his religious beliefs. While David and Charlotte tour the island together, Ramsay subtly encourages the crew to pressure David into pulling ashore in Honolulu to repair the ship, and then scours old newspapers until he finds an article identifying Charlotte as Inez Leidstrom, an escort accused of murdering a millionaire. That night, David and Charlotte kiss, and later he enters his office and finds Ramsay, who points out that the chronometer is broken, making it impossible for them to know their position at sea. The next day, Butterfield catches a fly, and after Wiggins accuses him of destroying the insect's life, the reverend muses aloud about whether his soul is pure. Relenting, Wiggins puts his hand on Butterfield's shoulder. The group then hears the crew pumping out water, and frightened, confront David, who agrees to dive under the ship to check the leak. He ignores the presence of a shark and re-boards safely, but when Anchor jumps in after him, the shark attacks the dog, and the crew knocks out David to keep him from jumping in to save him. He revives in his cabin with Charlotte nursing him, but Ramsay calls her away to reveal that he knows her true identity, then commands her to visit him that night. She sorrowfully remembers her time in Honolulu: Charlotte is left at the altar, forcing her to take work as an escort to support herself. Unknown to Charlotte, the escort service is a front to extort money from clients, and when one bribe attempt goes awry and owner Myra Pringle's goons kill a man, Charlotte is charged with his murder. In the present, she tries to reveal her past to David, but he is asleep. Later, when Harry asks Charlotte to befriend Ethel, she counsels him to marry her, even though he fears that his shady past will repulse her. Charlotte goes to Ramsay and starts to unbutton her dress, but when he kisses her, she bursts into scornful laughter and he pushes her away. In the morning, the crewmen bring David a letter of formal protest about putting in for repairs, but he remains adamant that they not stop in Honolulu. Ethel then overhears Ramsay advise the crewmen to "get rough," and informs Charlotte. Later, one of the men drops a spike near David's head, after which Charlotte informs him about Ramsay, proving his suspicions. When he confronts Ramsay, however, the mate reveals Charlotte's past and convinces him that, because she is wanted for murder in Honolulu, she will do anything to avoid stopping there. The pump then breaks irreparably, and a dejected David is forced to change course to Honolulu. That night, David smashes a bottle of whiskey to keep from drinking it. Charlotte enters his cabin and confesses that she will go to prison if she enters Honolulu, because although she married Mr. King so that he would put up bail, he was an alcoholic, and she fled the island to escape him. Over the next days, the ship slowly fills with water, and the passengers join the crew in doing everything they can to keep it afloat. David soon earns the crewmen's respect for his hours of work, but when another sail breaks, he worries that they will not make it. Finally, he admits to Charlotte that his last ship sank, and after she notes that they have both made mistakes they would like to forget, he praises the crew and passengers for having restored his faith in human nature. When a storm hits, the ship is nearly lost, but David's quick action saves them, and as they near Hawaii, they raise distress flags that are soon sighted by a cruiser. When the rescue team arrives and scoffs at the broken-down Cannibal , the crew is quick to defend her. After the passengers bid their fond farewells to the captain, the authorities detain Charlotte, and David pulls her aside to promise that he will return for her as soon as her two-year jail sentence is served. Salvage experts then offer David $300 to destroy the ship, and in response he sails the brigantine out to sea and sets her on fire, so she can "go down with dignity." Although his shipmate Old Brown worries that David now has nothing, he replies that he has nineteen dollars and a date in two years.
