A police detective uses the only witness to a gangland murder to smoke out the mobsters.

On a sleepy Sunday afternoon in Miami, Florida, criminal attorney Raymond Sheridan offers to pay lobbyist Oliver Tubbs $1,000,000 to direct a campaign to legalize gambling in Florida. Meanwhile, at the Miami police Homicide Department, Lt. Bart Scott tells his superior and good friend, Capt. Harry Elkins, that he plans to retire in two years. Bart then goes home to have dinner with fiancée Anne Easton and her young son Stevie. Anne, whose police officer husband was killed in the line of duty, has refused to marry Bart until he retires from the force. While Anne prepares dinner, Elkins receives an anonymous tip about a stabbing at the Cromwell Hotel and goes to investigate. Bart's tranquil evening then comes to an abrupt end when he is notified that the dead body of Elkins and that of an unidentified gunman have been discovered at the Cromwell. Hurrying to the hotel, Bart learns that a woman was seen running out of the room just after the murders. Meanwhile, Morrie Pell, the hotel assassin, reports to his employer, Sheridan, that Lila Hodges, the slain gunman's wife, witnessed the killings, prompting Sheridan to order Pell to kill her, too. After the dead man is identified as Joey Hodges, a triggerman working for gangster Louis Ascot, who runs a gambling organization in Havana, Bart realizes that the woman seen fleeing the scene must be Joey's wife Lila and deduces she must have sought refuge with Louis in Cuba. Upon arriving in Havana, Bart drives to Louis' villa and announces that he plans to take Lila back to Miami as a material witness. Lila is reluctant to go until Pell takes a shot at her and misses, convincing her that it would be safer to be in police custody in Miami. When both Louis and Lila refuse to reveal what Joey was doing in Miami, Bart decides to intimidate them into talking. Rather than taking Lila directly back to Miami, Bart squires her around town, making her a target. After Lila is shot at once again, Bart, aware that Louis has long been in love with Lila, tells the gambler that he plans to make Lila a walking target until his questions are answered. Lila's peril compels Bart to reveal that Joey was in Miami to put an end to the push for legalized gambling in the state. Louis then discloses that Sheridan has hired Tubbs to advance his interests and was responsible for Joey's murder. Bart escorts Lila back to Miami, but when she is poisoned on the flight home, Bart decides to make Sheridan believe that Lila is dead so that he will lower his guard. After publicizing Lila's death, Bart secludes her in his cabin in the Everglades, along with Anne, Stevie and police officer Tim Grogan. Sheridan, meanwhile, uses bribery and blackmail to accelerate his campaign, but Tubbs balks when Sheridan forces him to blackmail Harry Tremont, an upstanding citizen, into supporting his campaign. After Tremont refuses to capitulate, Sheridan orders him killed. When Louis discovers Lila's hideout in the swamps, Bart, concerned that Sheridan's thugs may have followed Louis, conceives of a plan to flush out Sheridan. After Bart brings Tubbs in for questioning about Tremont's murder, he deliberately switches on the intercom, then walks out of the office to confer with the police chief. In the adjacent office, Bart tells the chief that Lila is alive and able to link Tubbs to Sheridan. As soon as he is released, Tubbs informs Sheridan what he has heard. After instructing Tubbs to leave the country immediately, Sheridan sends Pell and his thugs to kill Lila. Having tailed Louis on his boat trip through the Everglades, Pell realizes that Lila must be hiding there and hires a boat captain to take them into the swamps. Before departing, the captain alerts Bart, and Bart then phones Grogan to warn him about the killers' arrival. As Bart hands out guns to Lila and Anne so that they can defend themselves, Lila becomes hysterical, but young Stevie's courage steadies her. When the captain stalls for time to allow the police boat to catch up, Pell becomes impatient and orders him to speed up. When the thugs dock, Lila, Grogan and Anne fend them off with their weapons, Soon after, Bart and reinforcements arrive and apprehend Pell and his gang. As Bart and Anne embrace, Lila shyly links her arm through Grogan's. At Sheridan's villa, the police find Sheridan shot dead, and a dazed Tubbs sitting across from him, gun in hand.