Cosmetics queen Viveca Scott (Vera Miles) has developed a seemingly magic wrinkle remover, but her former lover, Karl Lessing (Martin Sheen), a chemist for her company, knows the formula and intends to sell it to Scott's rival, David Lang (Vincent Price). Lessing refuses to sell it back to her at any price, and when he taunts Scott, she bludgeons him to death and covers up her tracks as best she can. Lang's secretary, Shirley Blaine (Sian Barbara Allen), has been giving information to Scott about his operation, and, knowing about Lessing's negotiations with Lang, she attempts to blackmail Scott. So Scott kills her too.

Final clue/twist: Columbo notices Viveca itching and, as he suffers in the same way, he realizes they both have poison ivy and must have contracted it from the same source. Scott suspects the wrinkle remover is responsible for her itching. However, Columbo tells her the poison ivy was actually on the slide of Lessing's microscope, shards of which they both touched – he while examining the crime scene, while she could only have done it around the time that Lessing was killed.

There is a sly reference to the film Psycho, in which Miles appeared, when Scott claims to Columbo that she "couldn't even hurt a fly". It is very similar to a notable line said by the Norman Bates character in the 1960 film.

Wine connoisseur Adrian Carsini (Donald Pleasence) runs a small winery specializing in unprofitable but prized wines. He is about to be named the wine industry's Man-of-the-Year. His half-brother, Rick (Gary Conway), only wants to spend money on various hobbies and interests like sports and fast cars and has also been married several times. When Rick gets tired of Adrian's indulgences, he announces his decision to sell the land to mass producers of cheap, profitable wines. Adrian knocks him unconscious and leaves him to die in an airtight wine cellar. He travels to New York to accept the award and attend wine auctions, at the same time establishing his alibi. Upon his return, he concocts a scuba diving accident to explain Rick's death by suffocation. Julie Harris plays Adrian's formidable secretary, who realizes that Columbo suspects Carsini of killing his brother, and has plans of her own for Carsini.

Final clue/twist: Columbo realizes Carsini had locked Rick in the airtight wine cellar with the air conditioning turned off, and realizes further that this happened when a heatwave had struck Los Angeles. Columbo steals a very rare bottle of wine (Ferrier Vintage Port 1945) from Carsini’s cellar, and when he treats Carsini and his secretary to dinner, arranges for the restaurant staff to serve it to them. Carsini, upon tasting the wine, explodes in anger and berates the staff for exposing it to very high temperatures. Columbo tells Carsini that reminds him of the recent heatwave. Carsini realizes that all the wine in his cellar would have been spoiled in the heatwave, so that night he sets out to destroy all the bottles. A heart-broken Carsini is caught in the act by Columbo and confesses, expressing relief that at least he does not any more have to deal with his secretary, who had guessed the truth and was pressuring him to marry her.

Harry Stone (Ken Swofford), a campaign manager for Nelson Hayward (Jackie Cooper), is coercing the womanizing senatorial candidate to end his affair with his wife Vickie (Joanne Linville)'s personal secretary Linda (Tisha Sterling), which Stone regards as too risky during a campaign. Stone is also the mastermind of a publicity stunt that involves fabricating death threats against Hayward, to promote his tough stance against crime. Hayward uses this to his advantage: he lures Stone to his own beach house (while driving Hayward's car and wearing Hayward's coat), where the candidate shoots and kills Stone, making it look like a case of mistaken identity at the hands of the phantom assassins.

Final clue/twist: Hayward, realizing that Columbo is coming closer to solving the murder, stages a phony assassination attempt on himself. He fires a silenced gun through a balcony window into his private hotel room. He later gets rid of the gun. Hours later he returns to the room, ignites a firecracker to mimic a gunshot, and claims that someone has just shot at him from outside. When the police express shock at the brazenness of the alleged shooter, he feigns outrage at them doubting his word, and demands that the bullet be removed from the wall and analyzed. Columbo reveals that the ballistics of the bullet are already in, and that it indeed was fired from the murder weapon. He explains that after Hayward had been alone in the room (a time when he ostensibly was making phone calls), Columbo had searched it and found the hole in the window and the bullet in the wall. He had done this hours before Hayward claimed someone had just shot at him.

Joanne Linville plays Hayward's wife. A young Katey Sagal has a small role as a secretary. Her father, Boris Sagal, directed the episode.

Dr. Bart Keppel (Robert Culp) is a "motivation research specialist" at Impulse Research Labs who has become an expert practitioner of subliminal advertising (which involves inserting frames of an advertised product into the reels of a film, so viewers' subconscious minds react to what is pictured). Keppel's more lucrative sideline is blackmail: he takes pictures of married clients with attractive women he hired to get them in compromising positions. When his latest victim, Vic Norris, refuses to be blackmailed and threatens to expose him, Keppel plots to kill him. Keppel serves salty caviar at a reception he is hosting for his clients prior to showing them his latest promotional film. Subliminal photos of a refreshing drink are inserted into the film, which, when it is shown, lure Norris out of the screening room. Keppel is supposedly narrating the film as it is playing, but in reality the clients are hearing Keppel's voice playing from a tape recorder. When Norris is lured out, Keppel shoots him in the building lobby. Keppel has already set in motion a scheme to make it seem that the crime was committed by Norris's wife. Keppel's projectionist, Roger White (Chuck McCann), then discovers the cuts in the film and pieces together Keppel's scheme, forcing Keppel to murder him as well when Roger tries to blackmail him.

Final clue/twist: Columbo uses Keppel’s technique against him. He arranges to splice into a film, which Keppel will soon view, many subliminal cuts of images of Columbo closely searching areas where the murder weapon must be. On seeing the cuts, an alarmed Keppel rushes to his office to make sure the weapon is still where he left it. Columbo is waiting there, hidden, and when Keppel retrieves the evidence, Columbo is there to seize it.

This episode received the Emmy Award in the category for Outstanding Limited Series.

Publisher Riley Greenleaf (Jack Cassidy) decides to kill his prolific author Alan Mallory (Mickey Spillane), for the insurance and also to keep him from defecting to another publisher. He hires ex-con and avid homemade bomb enthusiast Eddie Kane (John Chandler) to do the job. While Greenleaf is getting drunk at a nearby bar, Kane walks into Mallory's office and shoots him. To cover his tracks, Greenleaf then kills Kane with one of his own bombs, making it look like an accident. Columbo must discover the link between the two crimes.

Final clue/twist: Greenleaf hands over an old synopsis to Columbo, claiming it was Kane’s, which allegedly proves that Kane had the idea for Mallory's latest book, and murdered him out of revenge for Mallory's having stolen it. Columbo finds out, however, that the ending of the book was actually developed very shortly before the murder, by Mallory and his agent (played by Mariette Hartley), to make sure the book was more appealing for a Hollywood film adaptation. Kane could not have known the new ending, so the synopsis must have been done by Greenleaf.

This episode has a split screen of Greenleaf's alibi and Mallory's murder. Mariette Hartley's role is similar to the one she played in Season 7's "Try and Catch Me". Spillane was the real-life author of Mike Hammer detective mysteries. Cassidy played the villain in three Columbo episodes: this one, Murder by the Book and Now You See Him...

When Dr. Howard Nicholson (Lew Ayres) threatens to expose Neil Cahill (Robert Walker Jr.) for plagiarizing a paper from a recently deceased scientist, Neil's father, Dr. Marshall Cahill (José Ferrer), director of a high-tech Pentagon think tank, kills Nicholson to protect his son's reputation. He programs a cybernetic robot codenamed MM-7 (Robby the Robot) to take his place overseeing a war exercise. The elder Cahill steals a car from the motor pool and drives to Nicholson's house. In the driveway, Cahill runs over Nicholson, then carries his body into the house, ransacking it to make it look like a burglary. To cover up damage the car received from the impact, Cahill backs his own car into it, with many witnesses to the accident. Jessica Walter plays Nicholson's wife, who happens to be Neil's psychotherapist. Robby the Robot guest stars as MM-7.

Final clue/twist: Columbo realizes early on that Marshall is the likely murderer after finding a burned match at Nicholson's home (Nicholson's wife doesn't smoke and Nicholson himself used a pipe lighter; therefore the match points to a cigar smoker, which Marshall is), but fails to unearth solid evidence against him. Columbo discovers that Marshall’s motive was based on his love for his son. Columbo frames and arrests the son, which causes the father to confess. This episode provides perhaps the most glaring example of Columbo using ethically dubious means to secure a murderer’s apprehension.

Gospel-singing superstar Tommy Brown (Johnny Cash) is hugely successful, but he is unable to enjoy the usual benefits of fame and wealth. His zealous wife Edna (Ida Lupino) can prove he had committed statutory rape with one of his backup singers, Maryann. She watches him carefully when he is touring, and even blackmails him into giving all the proceeds from his concerts to her ministry.

Tommy decides to kill Edna and Maryann. He drugs both women to sleep while piloting a small, private plane flying to Los Angeles, then parachutes from the plane before it crashes into desert mountains. Brown lands roughly, hurting his leg. He hides the parachute and lies down near the burning plane wreckage, making it seem like he was thrown clear in a tragic crash caused by flying through bad weather. The FAA investigator (John Dehner) is ready to rule the crash was an accident. Edna's brother, Luke (Bill McKinney) appeals to Columbo to consider the case a possible homicide, based on his mistrust of Tommy.

Final clue/twist: Columbo’s investigation leads him to conclude that Brown must have used a home-made parachute to jump from the plane in midair, which he then hid somewhere in the mountains. Columbo tells Brown that a boy scout troop will be scouring the mountains for the thermo bottle that contained the drugs. However, Brown seems unperturbed. At the airport before Brown is about to fly off to a concert, Columbo notices Brown taking his car rental keys with him onto the plane. Because he doesn't return the keys, Columbo concludes that Brown must be returning to Los Angeles. That night Brown drives up into the mountains and unearths the parachute, but he is caught bringing it back to the rental car by Columbo, hiding in wait. A relieved Brown asks Columbo if he's afraid to be alone with a killer; Columbo plays Brown's songs and says anyone who sings that well can't be all bad.

When Hugh Caldwell (Michael McGuire) accidentally kills his wife during a fight, he calls his friend and neighbor, LAPD Deputy Commissioner Mark Halperin (Richard Kiley). Halperin helps Caldwell cover up the crime, then forces him to assist the following night in the drowning-murder of Halperin's own wife (Rosemary Murphy), a wealthy heiress whose money Halperin covets. Halperin arranges the situation to make it seem that a cat burglar (Val Avery), who has recently been active in their neighborhood, is the culprit in both killings, and orders Columbo to tailor his investigation to that theory.

Final clue/twist: Columbo enlists the burglar's help in trapping the true murderers. Columbo creates fake files for the "burglary investigation" on which Halperin had ordered him to concentrate. While perusing the file, ostensibly to help Columbo, Halperin notes the burglar’s address. He hides jewelry taken from one of the murder scenes there, and shortly thereafter leads a raid on that apartment. Columbo confronts Halperin and accuses him of being involved in the murders. Halperin threatens Columbo’s job, and is triumphant when the planted jewelry is found in the searched apartment. However Columbo reveals that he himself is renting the apartment, that the burglar has no connection to it. Since only Columbo and Halperin knew that address, Halperin must have planted the jewelry there, which in turn means he must have been involved in the murders.

The first murder victim, Janice Caldwell, is killed before the episode begins, and is seen only as a corpse. The actress playing the part is unknown.