Andrew Morton is an attorney who made it out of the slums. Nick Romano is his client, a young man with a long string of crimes behind him. After he lost his paycheck gambling, hoping to buy his wife some jewelry, she announced she was pregnant, Later he finds her dead from suicide. When he turns again to robbery he's caught by a cop and Nick pumps all his bullets into him in frustration. Morton's appeal to the court emphasizes the evils of the slums.

Bill Saunders, disturbed ex-soldier, kills a man in a postwar London pub brawl. Fleeing, he hides out in the apartment of lonely nurse Jane Wharton. Later, despite misgivings about his violent nature, Jane becomes involved with Bill, who resolves to reform. She gets him a job driving a medical supplies truck. But racketeer Harry Carter, who witnessed the killing, wants to use Bill's talents for crime.

Prize-fighter Davy Gordon intervenes when private dancer Gloria Price is being attacked by her employer and lover Vincent Raphello. This brings the two together and they get involved with each other, which displeases Raphello. He sends men out to kill Davy, but they instead kill his friend. Gloria is soon kidnapped by Raphello and his men, and it is up to Davy to save her.

From the trial of the survivors, we flash back to amoral crook Ralph Cotter's violent prison break, assisted by Holiday Carleton, sister of another prisoner...who doesn't make it. Soon Ralph manipulates the grieving Holiday into his arms, and two crooked cops follow her into his pocket. Ralph's total lack of scruple brings him great success in a series of robberies. But his easy conquest of gullible heiress Margaret Dobson proves more dangerous to him than any crime...

Small-time crook Nick Bianco gets caught in a jewel heist and despite urgings from well-meaning district attorney D'Angelo, refuses to rat on his partners and goes to jail, assured that his wife and children will be taken care of. Learning that his depressed wife has killed herself, Nick informs on his ex-pals and is paroled. Nick remarries, gets a job and begins leading a happy life when he learns one of the men he informed on, psychopathic killer Tommy Udo, has been released from custody and is out for revenge against Nick and his family.

A down-on-his-luck ex-GI finds himself framed for an armored car robbery. When he's finally released for lack of evidence--after having been beaten up and tortured by the police--he sets out to discover who set him up, and why. The trail leads him into Mexico and a web of hired killers and corrupt cops.

Tough L.A. private eye Mike Hammer gives a ride to Christina, a frightened young woman he finds running along the road one night. His car is run off the road by unseen thugs. Hammer is knocked out and Christina is tortured in an unsuccessful attempt to get information from her. They are put back into Hammer's car which then is forced off a cliff. Hammer wakes up in the hospital. Velda, his trusty secretary, informs him that Christina is dead. Pat Chambers, Mike's policeman friend, tells him to stay off the case, but Mike thinks it might be a big story--meaning big money for him--because the FBI is interested. He, Velda, and Nick, his garage mechanic friend, start investigating in hopes of finding out why Christina was killed.

Frank McCloud travels to a run-down hotel on Key Largo to honor the memory of a friend who died bravely in his unit during WW II. His friend's widow, Nora Temple, and wheelchair bound father, James Temple manage the hotel and receive him warmly, but the three of them soon find themselves virtual prisoners when the hotel is taken over by a mob of gangsters led by Johnny Rocco who hole up there to await the passing of a hurricane. Mr. Temple strongly reviles Rocco but due to his infirmities can only confront him verbally. Having become disillusioned by the violence of war, Frank is reluctant to act, but Rocco's demeaning treatment of his alcoholic moll, Gaye Dawn, and his complicity in the deaths of some innocent Seminole Indians and a deputy sheriff start to motivate McCloud to overcome his Hamlet-like inaction.