Columbo (season 5)

When elderly physician Henry Willis (Sam Jaffe) refuses to finance a return to the spotlight for his wife, aging former movie star Grace Wheeler (Janet Leigh). She kills him in his sleep, passing it off as a suicide. The elderly butler (Maurice Evans) believes Grace was in a private screening room the entire time, watching one of her classic films.

Final clue/twist: Because of a discrepancy between the actual runtime of the movie, Grace Wheeler watched during the murder and the real time is was running, Columbo can prove that there was a long enough time gap (caused by a ripping of the film) for Grace to do the murder.

This is the only episode where the murderer is not arrested, as Ned Diamond (John Payne), her longtime song and dance partner, falsely confesses to save Grace, after Columbo points out to him that she is dying of a brain disease {ironically the reason her husband refused to finance her return} and doesn't even remember the murder. Columbo has no choice but to arrest Diamond, both realizing that by the time he is cleared, Grace will have died after spending her last days living happily in the past.

Hassan Salah (Héctor Elizondo), chief diplomat of the Legation of Suari, an Arab nation with a new young king, has a scheme for shifting power within his government. He enlists Rachman Habib (Sal Mineo), a naïve idealist in the Legation, to help him stage the murder of a security officer, then plants evidence to make it look like the work of radicals. Salah pins the murder on the now-absent Habib, who, as part of the plan, has gone into hiding. Columbo quickly unravels the truth, but finds himself stymied Salah's diplomatic immunity. Columbo then meets the new king, who is on a diplomatic visit to the United States, and impresses the young monarch with his theories about the case.

Final clue/twist: Columbo gets Salah (still under diplomatic immunity) to confess the murder with his monarch in the next room listening. To stay in the U.S. rather than face Suarian justice, he waives his immunity from prosecution.

A CIA operative code-named "Geronimo" (Leslie Nielsen) recognizes the man he was sent to cut a deal with, speech-writing consultant Nelson Brenner (Patrick McGoohan, who also directed), as a CIA double agent from the past. This forces Brenner to kill Geronimo before Brenner's true identity is exposed. Columbo finds himself blocked at every turn by a man accustomed to keeping secrets, and even by a visit from the Director of the Agency (David White).

Final clue/twist: Brenner's alibi (a taped speech for a client) becomes irrelevant when Columbo can prove that some statements Brenner made in it were based on news that were broadcast for the first time hours after the recording was allegedly made.

Retired and renowned matador Luis Montoya (Ricardo Montalban) is a Mexican national hero. His trusted bookkeeper, Hector Rangel (Robert Carricart)'s son Curro is also a bullfighter. When Curro (A Martinez) is gored in the bullring, Montoya freezes up in fear and does not challenge the bull. He later decides to kill Hector, who knows what happened. Montoya lures Hector to the ring, where he shoots him with a tranquilizer gun, and unleashes the bull on the prone man. The result is that it appears Hector tried to take revenge on the bull that gored his son. Columbo, who just happens to be in Tijuana for the weekend, is recognized by a the suspicious local chief of police (Pedro Armendáriz Jr.), who enlists Columbo's help.

The Great Santini (Jack Cassidy) is a magician extraordinaire at a cabaret being blackmailed by his insatiably greedy employer, impresario Jesse Jerome (played by Nehemiah Persoff), who has learned that Santini is, in fact, Stefan Mueller, a former Nazi SS prison guard. Mueller tires of the arrangement and kills his blackmailer in the middle of his famed water tank escape act, giving himself what he believes to be an airtight alibi. He sneaks out of a room where he hides during the act, makes his way through the cabaret's kitchen dressed as a waiter up to the boss's office, shoots him, then returns to his act without anyone noticing. Robert Loggia plays Harry Blandford, the club's maître d' and less than enthusiastic business partner of the murder victim, whose personality was such that another character says of him, "To know him was to detest him."

Final clue/twist: Santini is undone by the used carbon ribbon on an IBM Selectric typewriter. Because the carbon ribbon has a clear imprint of everything written with it, it also has an imprint of the letter, the victim was typing - revealing the motive for the murder.

Commodore Otis Swanson (John Dehner) is a retired naval officer who owns a shipbuilding company, and is not happy with the shady dealings of his son-in-law Charles Clay (Robert Vaughn), who has turned the modest and upstanding business into a name-brand production line for status-seekers. Nor is he pleased with any of the people closest to him -- his alcoholic daughter Joanna Clay (Diane Baker), his middle-aged playboy nephew Swanny Swanson (Fred Draper), his lawyer Jonathan Kittering (Wilfrid Hyde-White), and his ship yard manager Wayne Taylor (Joshua Bryant). He announces at his birthday party his intention to sell the company. That night, someone murders the Commodore. Although we don't see the murder on-screen, Clay is seen covering up the death by taking the Commodore's body out on his yacht at night and throwing it overboard. Columbo investigates with the help of a veteran sergeant and a 29-year-old novice. The detective's conviction that Clay committed the crime proves premature and inaccurate, an unusual development for Columbo. Clay himself turns up dead and Columbo realizes that someone else is responsible for both murders.

Final clue/twist: When Columbo holds the pocket watch of the deceased commodore to every suspect's ear, only Swanny seems to be confused - because he broke the watch during the murder to create a false timeframe. He knew that the watch was supposed to be broken.