During one of her last scheduled crossings, the Claridon , a huge, old luxury liner, has a fire break out in her boiler room. The fire soon spreads to a dining room, but although some of the officers want to alert the passengers to the potential danger of the situation, Capt. Robert Adams insists that they act as though nothing has happened. Meanwhile, Cliff and Laurie Henderson and their young daughter Jill are enjoying their first ocean voyage, a trip occasioned by Cliff's job transfer to Tokyo. The fire is put out, but the next day, crew members notice that boiler pressure has greatly increased and that because of the fire, several safety valves have been fused shut. Chief Engineer Pringle orders the crew members out of the boiler room, knowing that if he is unable to release the safety valves, the resulting explosion will lead to his death. As he strains to pry open a valve, a huge explosion rips through the boiler room and many of the decks situated above it, killing Pringle and several passengers. Laurie is pinned beneath a fallen steel beam that Cliff is unable to move, and little Jill finds herself trapped on the far side of their cabin. While trying to rescue her, Cliff nearly falls through the gaping hole in the cabin floor. On the bridge, the captain ignores the warnings of First Officer Osborne and decides that as long as the bulkhead holds, the passengers are in no danger. Cliff eventually rescues his terrified daughter, and as the captain finally sends out an S.O.S., he leaves his trapped wife to find help. Cliff tries to locate an acetylene torch with which he may free his wife, but the crew members are too occupied with the task of shoring up the bulkhead to be of any help. Eventually Cliff encounters Hank Lawson, a black member of the boiler room crew. Hank agrees to help Cliff, but they are unable to locate an acetylene torch. The bulkhead finally blows apart, and a number of Second Engineer Walsh's men are killed. Laurie tries to convince Cliff to take Jill and get off the ship, but although he agrees to put the child on a lifeboat, he insists on remaining by his wife's side. When Laurie learns that the ship is being abandoned, she asks Hank to help her commit suicide, but he refuses. Hank finally puts Jill, who is screaming wildly for her mother, on a lifeboat, asking the passengers to send a torch back after the approaching Hawaiian fishing boat picks them up. Capt. Adams orders Walsh to help Cliff, but the engineer, whose father died on the Titanic , decides to save his trapped men instead. Walsh accuses the captain of sacrificing lives in order to secure his own promotion, because he knows that if the ship had reached its destination intact, the captain would have been proclaimed a hero. The accusation breaks the captain, and he retreats to his office, where he is killed by a falling smokestack. As water fills Laurie's cabin, the lifeboat returns with the acetylene torch, and Hank, Walsh and Cliff begin to cut through the metal that has pinned her to the floor. She is freed just as the water covers her head. They all then reach the upper deck just as the ship is slipping under. After climbing into the lifeboat, Cliff extends his hand to Hank, declaring, "This is one guy I'm going to help aboard personally!"