Alex Benedict (John Cassavetes), the married conductor of the Los Angeles Philharmonic Orchestra, murders his mistress, Jenifer Welles (Anjanette Comer), after she insists on going public with their affair, and tries to make it look like a suicide.
This episode marks the first appearance of Bob Dishy as Columbo's newly assigned and totally unwanted neophyte partner, Sergeant Frederick Wilson, full of the latest techniques from Berkeley.
Sir Roger Haversham (John Williams) realizes that actors Nicholas Frame (Richard Basehart) and his wife, Lillian Stanhope (Honor Blackman), have manipulated him into backing their theater production.
Columbo is visiting London to study British police techniques as the guest of Scotland Yard Detective Chief Superintendent William Durk (Bernard Fox), who is called to investigate the incident.
Sharon Johansen plays Miss Dudley, an attractive young understudy Frame has his eye on, and thus intensely disliked by Stanhope.
Final clue/twist: Police search the dead man’s closed umbrella, on exhibit in a wax museum, for a pearl from Lillian Stanhope's broken necklace, which would prove that Haversham visited her dressing room on the night he died, contradicting the couple's story.
When the umbrella is opened and a pearl is revealed, the increasingly unstable Frame starts babbling, and Stanhope tries to persuade Columbo that Sir Roger's death was unintentional.
Nurse Sharon Martin (Anne Francis), a friend of Hiedeman, who has never trusted or liked Mayfield, uncovers a suspicious piece of suture, which she takes with her from the operating room.
The hearing impaired Clayton tricks Dudek into writing what appears to be a suicide note and shoves him into a garbage grinder in the basement.
Flamboyant television chef Dexter Paris and his identical twin brother, conservative banker Norman (both played by Martin Landau), are supposedly not talking to one another.
But both disapprove that their uncle Clifford Paris (Paul Stewart) has become engaged to young, beautiful Lisa Chambers (Julie Newmar).
Clifford's lawyer, Michael Hathaway (Tim O'Connor) reveals to the twins that a new will exists that makes Chambers the lone heir of his dead husband, one which he is willing to "lose" for a price.
Instead, the brothers opt to frame Hathaway, who finds Chambers dead after an apparent fall from a window of her house, and make him look like the most likely suspect for their uncle's murder.
Jeanette Nolan plays Mrs. Peck, a sharp-tongued, fastidious, loyal housekeeper who is appalled by the "terrible mess" Columbo makes in the house.