A serial killer dubbed "Overkill" murders Mannix's old friend, but Mannix soon learns that the crime isn't as simple as the police believe.

A woman hires Mannix to fly to Arizona and pick up a package to deliver to the LAPD. But it turns out the woman has supposedly been dead for a month, and the package contains nothing but blank papers.

Heiress Cindy Conrad claims that she's receiving calls from someone claiming they have information on the death of her father years ago.

A woman whose legs were paralyzed in a car accident receives death threats and hires Mannix to investigate.

A mysterious businessman hires Mannix to find his missing son, a college basketball player.

Mannix's high school football team lures him to a ghost town on false pretenses for their reunion... but someone intends to kill them.

A young boy hires Mannix to protect his parents, who saw a gangster run over his girlfriend in a parking garage.

A police detective's wife hires Mannix to find out who wants to kill her husband... but doesn't want the PI to tell her husband who hired him.

Mannix's friend Paul Parrish goes to prison for a crime that Mannix doesn't believe he committed, and then kills his former cellmate after he's released.

Mannix wakes up with amnesia of what happened on the previous, and he and Peggy try to recreate where the PI was from the few belongings on his person.

George Hewitt hires Mannix to determine who is harassing his wife, and then dies in a car crash. Mannix talks to the widow, who denies anything about what her late husband claimed happened.

Ellen Grey hires Mannix to investigate what her recently suicided husband was involved with that drove him to his death. Mannix discovers that the people involved want Ellen dead as well.

A woman who claims to have precognitive powers tells Mannix that he'll soon be murdered. The PI is initially skeptical but soon comes to believe.

An attempt on a little girl's life convinces Mannix that she's telling the truth about witnessing killers plot their next murder.

Mannix' helicopter reporter friend dies in a crash, and the PI suspects foul play.

Mannix stops at a desert cafe on his way to a fishing trip, and runs afoul of three thugs holding the couple owning the place hostage. The PI escapes, but when he returns with the police, the couple claim nothing happened.

While in the hospital for a gunshot wound, Peggy falls in love with a neighboring patient... who is the new leader of an African country who is dodging assassins.

A widow hires Mannix to find her industrialist husband... who she says is still alive and has faked his death to avoid gambling debts.

A group of death-row prisoners take a guard hostage and demand\that Mannix prove one of their own innocent.

Mannix is searching for a missing brother, and injected with a slow-acting poison.

Someone takes shots at Mannix, but he suspects that a magazine photographer is the real target.

Mannix tries to clear the name of a boxer accused of murdering a fight fixer.

After apparently killing a burglar and taking the stolen goods for himself, Mannix loses his PI license and takes a job for a mob widow.

Mannix investigates the murder of the niece of one of his old Army buddies, and figures out that another member of his squad is responsible.