Columbo (season 7)

Mystery author Abigail Mitchell (Ruth Gordon) is convinced that her nephew-in-law, Edmund Galvin (Charles Frank), murdered his wife (Mitchell's niece) in a boating "accident" and got away with it. Mitchell asks him to retrieve something from her airtight walk-in safe, then locks him in it before flying off to New York.

Final clue/twist: Columbo eventually solves the case by piecing together clues left by Galvin as he suffocated in the safe. The most incriminating is the title page of Mitchell's new manuscript, altered to read "I was murdered by Abigail Mitchell". At the end of the episode, Mitchell notes that had Columbo been the one to investigate her niece's death, "none of this need ever have happened". Gordon's character is perhaps the most sympathetic killer caught by Columbo and he seems genuinely sorry to have to arrest her.

Paul Gerard (Louis Jourdan) is a renowned restaurant critic, but he runs a lucrative side business where he extorts restaurant owners in return for good reviews. When one of them, Vittorio Rossi (Michael V. Gazzo), refuses to pay, Gerard kills him with a bottle of wine poisoned with fugu.

Final clue/twist: Columbo figures out that Gerard poisoned the needle of the bottle opener, not the pressure cartridge itself. He tricks Gerard into an attempt to poison him in the same way, but he swaps the glasses in time. Assuming Columbo just poisoned himself, Gerard confesses. Columbo later also states that he suspected Gerard right from the beginning because Gerard didn't rush to a hospital to be checked after he learned that the man he just had dinner with was poisoned.After Columbo gets the goods on him, he asks Gerard what he thinks of a meal he has just prepared, and the charming murderer says, "I wish you had been a chef".

Richard Dysart and France Nuyen also star. Antony Alda (son of veteran actor Robert Alda) plays Rossi's nephew, Mario, who speaks only Italian. Falk's real-life wife Shera Danese returns as Gerard's secretary/treasurer/mistress Eve Plummer.

West Coast television production boss Mark McAndrews (Laurence Luckinbill) is promoted to a high-level position in New York. He fails to name his lover and logical successor, TV programmer Kay Freestone (Trish Van Devere), as his replacement, since he believes as a professional that she's not ready for the responsibilities. Her consolation prize is a new Mercedes. She is more interested in a gun he holds while jokingly inviting her to shoot him. Freestone takes him up on it during an important preview for a new made-for-TV movie called "The Professional" that she helped produce. She tricks the projectionist (James McEachin) by fiddling with the projector's timer and then sends him on an errand. Freestone sneaks up to McAndrews's office and shoots him, then returns to make the reel change successfully before the projectionist gets back. Patrick O'Neal plays Frank Flanagan, her boss. Van Devere's real-life husband George C. Scott has an uncredited cameo as a technician.

Mind control (or, as the doctor corrects the detective, "life control") seminar guru Dr. Eric Mason (Nicol Williamson) uses two trained Doberman Pinschers, Laurel and Hardy, to savagely kill his "best friend" Dr. Charlie Hunter (Joel Fabiani), who had been having an affair with Dr. Mason's now-deceased wife. Kim Cattrall plays the resident of Mason's guest house who discovers the body.

Joe Devlin (Clive Revill) is a renowned Irish poet, author, raconteur, and terrorist supporter. He, along with his own family and the heads of O'Connell Industries, is secretly a fund-raiser and gun-runner for the Irish Republican Army. He raises money in Los Angeles for his radical cause through a charity ostensibly meant to help victims of terrorism. Devlin has a strong belief in honor. Thus, when Vincent Pauley (Albert Paulsen), an arms dealer selling guns to Devlin, tries to skim off $50,000 for himself, Devlin shoots and kills Pauley for being a traitor. With Columbo hot on his trail, Devlin must find more guns and arrange their shipment out of the country.

Final clue/twist: Columbo discovers, that a bottle of whiskey at the crime scene has the same markings Devlin uses to make in his presence prior. Because every diamond has a unique cutting habit, Devlin's ring is proof of his presence at the crime scene. As for Devlin's illegal gun shipment, customs agents originally search the ship, but do not find it. When the ship is pulling out of the harbor, Columbo spots the tugboat flying an O'Connell Industries flag, and thus deduces that the guns were actually on the tug, and that they will be transferred to the ship just before it pulls out to sea.