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 friend from the old neighborhood asks Mike to travel to Chicago to claim the body of her son. While visiting the Windy City, Mike learns that the young man was murdered and the police don't appear to be interested in investigating the crime. When Mike visits the murdered man's room to pick up his personal effects, he is attacked and brutally beaten by a pair of thugs who want to know where "it" is. Mike has no idea, but he's determined to find out and make the two goons who attacked him which they'd never been born.

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".

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.

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 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 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.

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.

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'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 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 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.

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.

Doc Fawcett hires Mike to find the person to whom he's paying protection money. He's received letters that threaten his daughter, a high-wire acrobat, will suffer a serious, if not fatal, accident unless $500 is paid every month. When the leading suspect, Lou Lindsay, is shot with Doc's gun, Mike has no shortage of suspects - Doc hated the man because he made unwanted advances towards his daughter; the girl's would-be boyfriend had been severely beaten by the roughneck, Lou had made loved than dumped have the women in Doc's carnival and the cuckolded husband of one of the women ran the carnival's shooting gallery.

A pretty secretary swims across the lake to the cabin Mike has rented for vacation and invites him to a party at her uncle's estate. The party soon loses its appeal when Mike bumps into an old adversary, a lawyer who claims Mike railroaded his client by faking evidence. When the lawyer is accused of murdering his host, Mike shows the value of a fake identification to smoke out the real killer.

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.

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.

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.

Hammer is hired by Susan Barlow but she stands him up. He investigates and runs into her husband Hank Barlow. After a fight, Hank hires Hammer to find his wife who has been missing for several days. Hammer talks to Shelton Dean of the brokerage firm Haskell & Dean, who had called Mrs. Barlow. Haskell is a recluse and Mrs. Barlow is claiming to be his daughter.

While getting a shoeshine in the Bowery, Mike spots a beautiful, well-dressed blonde who is as out of place as a field of wildflowers growing out of a crack in the concrete. When the woman is mugged in an alley, Mike comes to her aid and learns that she's searching for her husband, a blues piano player, who hasn't written to her in Wyoming in over a month. Mike traces the missing husband to a penny arcade and then follows the bodies to a fashionable apartment uptown.

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.

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.

Mike's girlfriend, Jackie, a dancer in a chorus line, panics when a sleazy reporter points out the similarities between a pair of chorus line murders and the Jack the Ripper killings 70 years ago - both of the murdered girls were redheads and Jackie is the only redhead left in the troupe. Mike has two suspects - a doorman who hates actresses and the reporter who may be making the news instead of simply reporting it.