A returning veteran tangles with a ruthless gangster during a hurricane.

Disillusioned veteran Frank McCloud arrives on the island of Key Largo, Florida to visit the family of George Temple, who died under his command in Italy during World War II. At the rundown Hotel Largo where George's wheelchair-bound father James lives with George's widow, Nora, Frank encounters Curly Hoff, Toots, Angel and Gaye Dawn in the bar. Learning from them that the hotel is closed for the off-season, Frank searches out the Temples, who greet him warmly and insist that he stay the night. Nora explains that their guests offered her father-in-law so much money to open the hotel for them, that he could not turn them down. Later, a hurricane warning is issued and as Nora fastens the shutters in preparation, the telephone rings. Curly tells the caller that the Temples are not around and adds that Sawyer, the local police officer, has not been seen either. When Temple objects, the men pull their guns. In response to the activity, the men's leader comes downstairs for the first time since Frank's arrival, and Frank recognizes him as deported gangster Johnny Rocco. Rocco has entered the country illegally from Cuba in order to make a delivery of counterfeit money, but his contacts have been delayed by the approaching storm. Meanwhile, he and his men have captured and beaten Sawyer, who was searching for the Oceola brothers, Seminoles who had escaped from jail. When Rocco, impressed by Nora's feisty spirit, makes a pass at her, she spits in his face, and Frank stops him from killing her with some fast talking. Mocking Frank's heroics, Rocco throws him a gun and, holding his own gun on Frank, tells him that he can rid the world of Rocco if he is willing to die in the process. To the disappointment of both Nora and Temple, Frank refuses to shoot. He throws the gun down and Sawyer grabs it and tries to escape. Rocco kills Sawyer, revealing that the other gun was not loaded, a fact that Frank had no way of knowing. Rocco then demands that Gaye, his alcoholic former mistress, sing a song before she can have a drink. She is too desperate to sing well, and when Rocco still refuses to give her a drink because her singing was "rotten," Frank takes pity on her. Rocco slaps him and once again, Frank does nothing. The full force of the hurricane then hits, terrifying Rocco and giving Nora a chance to challenge Frank about his disillusionment. After the storm passes, Rocco discovers that his boat has disappeared. He orders Frank to take Temple's boat and transport him to Cuba. Before they can leave, a second police officer comes looking for Sawyer and finds his body on the shore, where it washed up during the storm. Rocco blames the murder on the Oceola brothers, who are on the island to turn themselves in on Temple's advice, and when the Indians try to escape, the officer murders them. As the gangsters prepare to leave, Gaye begs Rocco to take her along, and while she clings to him, she grabs his gun from his jacket pocket and slips it to Frank. After he sets course for Cuba, Frank maneuvers the boat to knock one man overboard and shoots the others, including Rocco. Although he has been wounded, Frank radios his position and then calls the hotel to tell Nora and Temple that he is coming back home.