Temperamental artist Max Barsini (Patrick Bauchau) effectively lives with three women: his ex-wife, Louise (Fionnula Flanagan), his young live-in model Julie (Isabel García Lorca), and his current wife Vanessa (Shera Danese). Barsini takes delight in the way they fight for his attention. But when Louise begins seeing a therapist, Dr. Hammer (George Coe), who is also her new fiancé, Barsini fears she will reveal that he killed his first agent, who was robbing him. He kills Louise, then makes it look like she drowned at the beach while he was at Vito's bar, painting. Columbo poses for Barsini while investigating him.

When Dian Hunter (Deidre Hall), the partner of men's magazine publisher Sean Brantley (Ian Buchanan), vanishes after expressing a desire to sell her 51% interest to a rival, suspicion falls on Sean and his girlfriend Tina (Rebecca Staab). Columbo sets out to find the body, eventually digging up much of Brantley's estate and breaking open the walls. But after the search turns into a full-blown media event, Dian resurfaces, explaining she needed some time to herself. Dian and Sean planned the disappearance as a publicity stunt to increase sales. But to his shock, she actually intends to sell now that her holding is more valuable. Sean proceeds to then kill Dian for real and hides the body, believing that Columbo will not be allowed to search for it again.

Oscar Finch (Patrick McGoohan) is a lawyer who uses underhanded methods to get his clients off, like coercing Paul Mackey (Denis Arndt), who worked for the D.A.'s office, into destroying evidence against racketeer Frank Staplin (Louis Zorich) in 1969. Twenty-one years later, Mackey is chosen by a presidential candidate, Governor Montgomery (Arthur Hill), to be his vice presidential running mate. Finch himself hopes that he might be appointed as the next Attorney General. Staplin, facing another indictment, threatens to expose the long-ago favor and ruin Finch's and Mackey's political futures if he doesn't arrange the destruction of another document. Finch decides to murder him. He scatters cigar ashes to make it seem he was in a late-night meeting with a contributor when the murder occurred. Finch walks to Staplin's house, shoots him and makes his death look like a suicide.

Final clue/twist: After Columbo learns that Staplin hadn't eaten any of the cheese on the dish at the crime scene, but that the block of cheese had had a piece bitten off from it, he assumes that the murderer must have taken a bite. CSI can fabricate a toothprint from the cheese and Columbo finds more than enough samples of Finch's toothprint on his discarded pieces of chewing gum - proving that he was at the crime scene.

The episode, which uses the in medias res structure, opens at the funeral of Columbo's wife, and is partially told in flashbacks. Vivian Dimitri (Helen Shaver) is a real estate executive whose recently deceased husband had been sent to prison by Columbo. She seeks revenge by plotting to kill the Columbos. But first she murders her boss, Charlie Chambers (Edward Winter), her husband's partner who avoided prison by informing on him. Vivian shoots Chambers in his office, using her affair with the married Leland St. John (Ian McShane) to establish an alibi. Then she plants evidence to make it look like Chambers was killed by disgruntled residents of a new housing development he was constructing. Her plan is then to kill the Columbos with a jar of poisoned marmalade. Roscoe Lee Browne plays her psychiatrist, Dr. Steadman.

Final clue/twist: Figuring out Dimitri's plan, Columbo and the police fake the death of his wife. After staging the fake funeral, Columbo invites Vivian into what she thinks is his house. He makes himself toast with marmalade. While Columbo pretends to be dying of poison, Dimitri confesses to all three murders. He then reveals that he had suspected her all along, and had the marmalade tested as soon as she gave it to him. They are actually in the home of another officer, who recorded the confession, and the marmalade jar is a different one lacking poison.

Dentist Wesley Corman (James Read) decides to get rid of his unfaithful wife, Lydia (Jo Anderson), and use her money to support his gambling habit. When Adam Evans (Marshall R. Teague), a Hollywood heartthrob having an affair with Lydia, comes under his care, Corman puts a time-release poison made from digitalis under a crown. It takes effect when the couple are together that evening and Corman is playing cards, thereby framing Lydia for the murder. Paul Burke co-stars as Horace Sherwin, Lydia's father, also a dentist.

Final clue/twist: Columbo traps Corman by taking advantage of the fact that Corman was never good at chemistry. He orders Evans' body exhumed and demonstrates to Corman that if there was indeed digitalis, it would have caused a chemical reaction with the porcelain in the crown, making a blue stain on Evans' tooth underneath the crown. Before they begin to examine Evans' mouth, Corman confesses. However, Columbo was bluffing, as digitalis causes no such reaction with porcelain.

Jess McCurdy (Brenda Vaccaro) fails to convince her sister, best-selling romance novelist Theresa Goren (Janet Margolin), to cancel her wedding to Wayne Jennings (Andrew Stevens), a playboy/tennis bum half her age and a gold digger. McCurdy impersonates her sister on the phone with Jennings and dumps him. Jennings reacts by killing Goren - twice. He arranges an alibi for the first murder, then returns and shoots her corpse. He allows Columbo to "catch" him for the second murder, which he confesses, but then "learns" that he had only shot a corpse, so is innocent of murder, which he assumes will be blamed on a burglar.