When a man convicted of armed robbery is mortally wounded in a prison knife fight, he calls on Hammer to perform a last service - retrieve the loot he hid before he was arrested and use the money to ransom his wife who has been kidnapped.

When an elderly man living in Mike's hotel unexpectedly inherits $7500, Hammer appoints himself the man's guardian to ward off moochers and con artists.

After discovering his office has been ransacked, Mike receives a threatening phone call ordering him off "the case" and to drop his client, Sharon O'Closkey. Mike refuses, even though he wasn't working on a case and didn't have a client named O'Closkey. When the mysterious client calls and invites the private investigator to her room, Mike quickly agrees, only to fall victim to drugged meal. When he awakens, he discovers he's in Las Vegas and his beautiful client claims he flew to Nevada willingly to help her find her missing father.

At the behest of an old friend, Mike investigates her son's relationship with a beautiful young woman whose sugar daddy, a mobster turning states evidence, was murdered outside a nightclub.

Mike responds to a phone call from a small-time junkie requesting protection too late; he finds his friend shot to death in a Chinatown alley. Not satisfied that the police will exert themselves to find the man's killer, Mike launches his own investigation and links the crime to an earlier unsolved murder.

Mike returns to his old neighborhood when gunsels working for a protection racket murder a boyhood friend. Before long, his investigation into the gang's criminal activities results in more fatalities.

While eating in a hotel restaurant, Mike spots a man take a package from a woman's table. Even though the package contains a necklace with a broken clasp as the man claimed, Mike smells foul play and traces the woman who left the box. When he arrives at her house, he learns that she was pushed down her stairs and badly injured. Investigating further, he discovers she is the victim of a vicious blackmailer.

Mike investigates a dishevelled man's wild tale about a man that he killed six months ago dying a second time in a car accident two days ago. When his client turns up dead, Mike follows his only clue, the phone number of a pretty piano player billed as "Miss Patti".

Mike is hired to find the murderer of a newspaper reporter. The trail leads to a ballroom whose hostesses, usually small-town girls with no relatives, frequently disappear.

A nightclub singer asks Mike to get her out of a contract that's held by a mobster. The man claims the rising star who she owes him $50,000 "for expenses" plus 30% of her salary in perpetuity. While Mike is working on the contract, the singer receives a blackmail threat. Mike tries to retrieve the indiscreet photograph, he finds the blackmailers dead and the negative gone.

Mike is hired to retrieve incriminating letters from a blackmailer, but soon learns that the package with $50,000 was really the ransom money to payoff kidnappers. When the woman who collected the ransom from Hammer is double-crossed, she tries to get revenge on her partner but is killed before she can meet with the private detective. Hammer investigates the dead woman's friends and co-workers to mete out his kind of justice upon the kidnapping murderer.

The lawyer for a wealthy couple asks Mike to help their niece kick her heroine habit. Mike works on two fronts: helping the young woman withdraw from the drug and finding the pushers that got her hooked in the first place.

Mike is asked to investigate help a young man who has been arrested for murder in a small Pennsylvania town. He thinks the case against his client is pretty good, but when the local district attorney and deputy sheriff try to run him out of town, he decides to investigate further.

While waiting for his car to be repaired at a friend's combination garage/used car lot, Mike gets involved with three unsavoury characters who are very interested in a Jaguar sports car that has bullet holes in the back of the driver's seat with blood stains to match.

Taking a ferry ride in New York harbor, Mike sees a young woman crying. She's been victimized by a carnival con artist who charges steep fees to enter a rigged talent contest.

Mike's quest for peace and quiet is interrupted when he intervenes in a lover's quarrel fought in a swanky restaurant. The next day, Mike is hauled into court and forced to post a peace bond guaranteeing that he'll stay away from the man he fought with the previous evening. When the man turns up dead and his fiancée accuses Mike of the crime, Hammer has to go on the lam to clear himself of the frame-up.

Mike runs into an old acquaintance, the wife of an embezzler he helped send to prison, who asks for her help. When she turns up dead in her apartment, rather than in his office as scheduled, Mike investigates. He's curious why a blue-blooded lady should arrange to bury the wife of a convict and discovers that both women are involved in a shady escort service dabbling in blackmail.

A serial killer is carving up women in the neighborhood where Sam Earl, one of Mike's part-time assistants lives. The legman wants to help Mike capture the psychopath before he strikes again, but Hammer insists it's a job for the police department, until Sam's brother's fiancée is brutally stabbed.

Mike is asked to help a popular disk jockey who's been threatened by a powerful music producer to play her performers' songs or else. While Mike is trying to persuade the producer to back off, the disk jockey is brutally beaten, and Mike is fired as a result. When the DJ collapses from the injuries he's sustained, Mike decides he's been rehired and takes after the producer and her goons with a vengeance.

Mike discovers his girlfriend's roommate has been murdered and launches his own investigation. He discovers that she was killed for a diamond she was trying to fence and tracks the murderer to the Brussels World Fair.

A psychiatrist fears that his patients are being blackmailed. He hires Mike to find out if his fears are founded, how the privileged information is being leaked and who is preying on his clients.

A death row convict confesses to a murder that another man was executed for three years earlier and threatens to supply proof after his execution.

Mike is hired by a beautiful heiress to break up her father's romance with a much younger woman. Mike goes to the woman's apartment and, after interviewing her, decides it really is a May-December romance and determines to give up on the assignment. When a thug claiming to be Mike Hammer threatens the lovely lovebird with bodily harm if she doesn't give up her sugar daddy, Mike gets back on the case and investigates who would really benefit if the romance were scotched.

Working for the insurance company, Mike assists the police investigate an armed robbery of an armored car company. His investigation reveals that the sister of a crippled friend who only helped the hold-up gang because of the beatings they had given her brother. Mike can't capture the thieves without implicating the young woman.

A rich industrialist wants to hire Mike to beat up his son and heir because the young man has become engaged to woman considered beneath the family's standing. Mike turns the job down, but agrees to drive the industrialist to the family's cabin in the Catskills where the son and his fiancée are waiting out a storm. When Mike arrives, he finds the young woman dead, bloodstains on the floor and conflicting stories about how both occurred.