When the franchisee of a health club chain discovers the founder, Milo Janus, is cheating him. To keep him from going to authorities, Milo murders his partner, making it look like an accident in the gym.
When a scientist employed at a government institute threatens to explose plagiarism by a fellow scientist, the plagiarist's father, a director of a Pentagon Think Tank, kills the potential whistle-blower to protect his son.
Motivation research specialist, Dr. Bart Keppel, is an expert in subliminal advertising, but has a very lucrative sideline in blackmail. When one of his victims refuses to be blackmailed and threatens to expose him, Dr. Keppel uses subliminal cuts to lure his victim to his doom and frames the victim's wife.
Two chess grandmasters, Emmitt Clayton and Tomlin Dudek, play an impromptu game the night before a big match. When Clayton loses, he decides to murder Dudek by shoving him into a garbage compactor, but being deaf, doesn't realize the compactor's safety feature turns it off when something heavy enters. Clayton learns that Dudek survived and plans to poison him in the hospital before he awakens.
Two doctors have pioneered a major medical breakthrough in cardiac surgery. One, Dr. Mayfield, wants to publish immediately, but the other, Dr. Hiedemann, wants further testing. When Dr. Hiedemann's heart condition worsens, Dr. Mayfield sees his chance to murder the man that stands in his way by performing the required heart surgery himself with dissolving sutures. His nurse discovers his plot, so he murders her too and makes it look like a mugging perpetrated by her drug addicted ex-boyfriend.
An aging star feels threatened by the fiance of her personal assistant, an author writing a tell-all book about her. She schemes to kill the author, but accidentally kills her assistant instead. Columbo discovers the connection between this murder and the mysterious disappearance of the actress' husband years before.
When Sir Roger Havershame realizes that he has been manipulated into funding a theater production, he confronts the actors responsible and is killed accidentally during the argument. The couple haul his body to his estate and stage an accident to make it look like he died in a fall down the stairs. Columbo, who is in London to learn investigative techniques as a guest of Scotland Yard, becomes involved in the case.
When a war hero's accomplice in embezzlement decides to flee the country because the authorities are investigating, the General murders him to ensure his silence. The murder is witnessed from a boat by an easily manipulated young woman, whom the General tries to make doubt what she saw.
The CEO of a private security company tries his hand at blackmail, but his plan backfires when his victim, a publisher's wife, threatens to expose him and he accidentally kills her during a heated exchange.