Mike is hired by an ex-con who now runs an amusement park in New Jersey. The former con-artist has received blackmail notes demanding $25,000 or else he reveal that the old man lied about his identity on his business license applications.
An old friend asks Mike to reason with a young man who refuses to identify the murderers of a drugstore owner in his old neighborhood. Mike is no more successful than his sister or the police in persuading the youth to talk, but when the witness is found murdered the next day, Mike decides to bring in the killers on his own.
A woman hires Mike to find the man who murdered who father, an experienced steeplejack and window-washer who fell 20 floors to his death. Mike's investigation shows that the murdered man lost a $10,000 investment with a crooked stockbroker who seems to have disappeared, leaving a hulking henchman behind to protect his interests.
Hammer is providing security for a jewelry store and catches a woman stealing a piece. Her husband is a gambler deeply in debt and Hammer takes pity and decides to help her. Hammer poses as her cousin and discovers that the poker game her husband plays in is crooked.
Mike helps out an old friend when her husband is accused of murdering a loan shark. His investigation revealed that a number of people were interested in taking over the mobster's racket, but the crucial bit of evidence is the scent of cheap perfume Mike smells in the murdered man's apartment.
Sonya Miles, a pretty secretary, engaged to marry her wealthy boss's son, is threatened with blackmail by her sleazy ex-husband, a rodeo performer. She hires Mike to keep her former spouse in line. Mike reasons with the cowboy - using both of his fists - and thinks the situation is in hand, but the ex-husband forces Sonya to break into the office safe at night. When the cowboy is discovered murdered in the office, the money gone and Sonya's purse is found at the scene of the crime, only Mike believes in her innocence.
Mike's old friend Patricia Tyler calls him for help when neighborhood hoodlums vandalize her father's grocery store. Mike sides with the hoodlums since her father was the vote that hung a jury in the murder trial of Mike's nemesis, Sam Mayo, a gangster who Mike believes killed a friend of his. When the assistant District Attorney decides to drop the case because several witnesses develop amnesia, Mike starts his own investigation - with surprising results.
Vic Fontainee, a blind fish monger, hires Mike to find out if the man claiming to be his long-lost brother is really on the level. Mike discovers that not only is the man an impostor trying to falsely inherit $20,000 from the Fontanee family trust, but the fraud is also having an affair with his wife, Maria. What Mike doesn't discover, until it's too late, is Maria's plan to kill her husband.
Luke Lund is being blackmailed. He is a racketeer now posing as a legitimate land developer in Shale City. He lures Mike Hammer from New York and with the help of a crooked cop frames him for the murder of the blackmailer.
Mike receives an anonymous letter with a $300 retainer hiring him to investigate the disappearance of a parking lot attendant. Mike learns that the man was defrauding the owner by marking wrong arrival times on parking tickets and pocketing the proceeds. When the man was found murdered, he traces the killer back to the company's headquarters.
A beautiful Chinese woman asks Mike to find the man who robbed an illegal poker game held in the back of a Chinese restaurant. One of them who lost heavily has threatened her father, the restaurant owner, with bodily harm unless the money is returned within 24 hours. Mike's only clue is the masked gunman had the number "8" tattooed on the back of his left hand.
Mike, vacationing in France, is asked to help a pretty American widow who is traveling on the ocean liner "Isle de France". The woman claims to see her dead husband everywhere, but the ships' officers think she is slowing going insane with grief. Mike agrees with their diagnosis until he sees the "ghost" try to throw the widow overboard; he then races against time to capture the all-to-real spirit before he can finish the job.
Mike is hired to dissuade a pretty blonde from blackmailing his client with a tape recording of his extra-marital indiscretions. Mike finds the woman hanging from the ceiling in her apartment and, after his client is arrested for murder, investigates other parties who had reason to want the young woman dead.
Mike investigates a $50,000 jewelry heist and double-murder for the insurance company. He gets a tip that the thief and murderer is hiding in a nearby hotel and kills the crook in a gunfight. When Mike learns that the dead man was a known jewel thief who never carried a gun, he suspects that he was tricked into shooting a man by his double-crossing partner and sets out to bring the other gunsel to justice.
When several of Johnny Sixty's juke box machines and his ace mechanic murdered, the police focus on Sixty's business rival, Wallets Mack. Mack insists he's innocent and hires Mike to prove it. Mike's investigation turns up blackmail, an invalid wife and a pretty singer with dreams of the big time.
Mike is hired to discretely investigate a series of attempts on the life of Carl Kunard, a successful building contractor, the most recent of which took place at the man's vacation lodge in upstate New York. Mike's suspects include Kunard's unhappy business partner, his trophy wife and his resentful son. Hammer's efforts are hindered by a fraternity pledge held in the lodge to escape the prying eyes of the university authorities.
Hammer is hired by a gypsy to clear her boyfriend Carl as an accomplice in robbery. Carl's brother Van is a monkey grinder and after Hammer questions him is murdered. The monkey (Banjo) saves Hammer's life as he solves the crime and clears Carl.
Showgirl Ruby Duvall is roughed up by her future sister-in-law, arrogant society snob Joyce Conroy, and offered $5000 not to marry Philip and soil the family name. It seems an open-and-shut when Ruby is found dead in her dressing room after a visit from Joyce. It's all too obvious for Mike after learning of another backstage visitor that night: Ruby's violent ex-con ex-boyfriend who refused to let Ruby go.
A college girl comes to Mike saying her mother, an attractive widow, is involved with a man trying to con her out of money. Hammer confirms there are a couple of scams going on. One is being played on him by the daughter; the other involves betting on horses with the seemingly innocent characters doing the cheating.
Mike's vacation at the 1958 World's Fair in Brussels is interrupted by a case. Wealthy Wilma Puttnam asks Hammer to investigate the people claiming to have the daughter of her late sister who died in the Nazi concentration camps. Mrs. Puttnam wants to be sure it's really Anna/Derna before paying the $5000 they're asking for.
Tom O'Rough is severely beaten en route to Mike's office. He's concern that Si Loomis, a small-time crook, has won the heart of his employer, Edie Sanford, and she's about to lose her money and her company to the grifter. When Mike can't force the crook to back off and can't convince the Edie that she's fallen for a criminal, he tries to use Loomis' pretty young secretary to get enough evidence to break up the romance.
Mike finally meets the love of his life and proposes to attractive Kathy Dean. They never make it down the aisle; he and Pat Chambers find her shot to death just before the wedding. Learning from Gita that a bookie was offering 100 to 1 odds the wedding would never happen, Hammer goes on a violent rampage until he gets to the man behind the murder.
A dying man comes to New York and hires Mike to find the attractive young woman he remembers from 15 years earlier. Mike tracks down Sally Bryant to the fleabag Central Hotel and discovers she's hardly beauty the old man remembers. She's slovenly, hard-edged, and married to a greedy husband with a stripper girlfriend.
A married out-of-towner is set up for a mugging in Central Park by a sexy young woman he'd only met that day. Wanting his stolen briefcase back and his name out of the newspapers, the cheating husband comes to Mike for help. Ellen Robbins, who's still on probation, is running the mugging scam with her boyfriend and another thug. Matters turn deadly when she returns the briefcase for $1000 bucks and doesn't cut her cohorts in on the extra money.
Punch-drunk former boxer Kid Dakota still carries a torch for gold-digging his ex-wife Julie. The Kid got into a fight with Julie's current husband at their restaurant (which used to be his) and vowed to kill him. When the husband turns up dead a few hours later, the police have an open and shut case. Mike, however, thinks Kid's been framed by someone else who wanted the current husband dead.
An Asian nightclub singer is offered $5000 by her boyfriend's snooty society mother to just disappear. She turns it down until her husband, a Merchant Marine she escaped from long ago, shows up demanding cash to go away. She shoots him in self defense, but doesn't kill him. Mike believes her story and works to clear her of a murder charge.
Mike's slippery friend Al Sparks skips town because of a gambling debt. He turns up in Forge River charged with murdering the female owner of the diner where he worked. Hammer discovers everyone fears Todd Stryker, the man who runs his wife's huge lumber company and wields all the power in town. Stryker's relationship with the dead woman is a secret he wants to keep.