Private investigator Brimmer is test-firing a gun at a firing range. Once he finishes, he leave with his underlings, who report to him the status on his company's current cases. Brimmer goes to his office and prepares for a meeting with one of his clients, newspaper owner Arthur Kennicutt. While he waits, Brimmer contacts a woman in the next room and tells her to listen in carefully. When Kennicutt arrives, Brimmer tells Kennicutt that he's kept his wife Lenore under surveillance for the last five weeks, per his request. He assures Kennicutt that Lenore has been faithful to him. Kennicutt is surprised, but admits that he's angry at himself for marrying a younger woman and becoming paranoid.
Once Kennicutt leaves, Brimmer meets with the woman in the next room: Lenore. She's not sure what he wants, and Brimmer explains that he lied to her husband and falsified the report. He knows she was having an affair with a golf pro, Ken Archer. Lenore tells him that it's over and it was a stupid mistake. She wonders why Brimmer didn't tell Kennicutt the truth, and he claims he believes in marriage. However, when she thanks him, Brimmer says that he wants her to provide inside information to help his agency. She hesitates and he tells her to think about it.
That night, Brimmer drives home and finds Lenore waiting for him. She explains that she and her husband have a beach house three miles away, and she walked down and then came in through the open terrace door. Lenore wonders how many other rich men's wives he's blackmailed, and then tells him that she won't give in. When Brimmer threatens to call her husband, Lenore says that she'll tell Kennicutt himself. She's willing to accept the consequences, but she warns Brimmer that Kennicutt will despise the investigator for lying to him. As she goes, Brimmer grabs her and she fights back. Losing his temper, he hits her across the face with his left hand and she falls back, hitting her head on a table.
Once he confirms that she's dead, Brimmer goes to work covering up the crime. He wipes down her fingerprints, removes her jewelry, and then puts the body in the trunk of his black Cadillac Eldorado. Brimmer drives to a construction site and dumps Lenore's body and then leaves.
The next day, Columbo is driving to work when a traffic cop pulls him over for a faulty turn signal. Once he realizes that Columbo is a police detective on his way to a murder, he lets him go after warning that his license will expire next week. The traffic cop provides him with an escort to the construction site. The medical examiner is fairly sure that the body was moved after death, and suffered from two wounds. Columbo is busy looking for a match to light his cigar. While the detectives confirm that Lenore was apparently robbed. They confirm she was married to Arthur Kennicutt, and worry that he'll use his newspaper to condemn them if they don't find the killer. Columbo examine the bruise on the left cheek with some interest.
At the morgue, Kennicutt confirms for Columbo that the dead woman is his wife. The detective gets him a cup of coffee, and the publisher immediately confirms that he has an alibi. Kennicutt then tells Columbo to find the real killer, and soon. He insists that his wife had no enemies, and that she was faithful to him. Kennicutt does note that his wife played tennis. As Columbo goes, Kennicutt tells him that he married a younger woman and their marriage worked, and warns Columbo that he doesn't plan to be patient with the investigation.
Later, Columbo meets Kennicutt at his home and admits that there hasn't been any progress yet. The common theory is that Lenore was mugged, but they can't explain why the body was moved. Columbo thinks that Lenore knew her murderer. She went out to the beach house in the middle of the week, went for a walk, and then turned up dead on the other side of town. The detective wonders if Lenore had any problems, and Kennicutt insists that she was a happy woman. Kennicutt isn't satisfied with the progress of the investigation and introduces him to Brimmer of Brimmer Associates. Brimmer has met the police commissioner and knows about Columbo. Kennicutt informs the detective that he's hired Brimmer to find his wife's killer. Brimmer is eager to assure Columbo that he is there in an advisory capacity, and the police authorities have okayed his involvement. Columbo is more interested to learn that Brimmer has worked for Kennicutt on a personal matter. Columbo starts talking about palmistry and checks Brimmer's hand. As Columbo leaves, he inadvertently walks into a closet by mistake and notices a bag of golf clubs. He confirms that they belong to Lenore and that she just started playing at the country club. When Columbo wonders why they're not at the club, Kennicutt explains that she took lessons elsewhere. As Columbo goes, he walks past Brimmer's car and notices the chrome is tarnished.
At the club, Ken Archer is giving lessons to an attractive woman. When he finishes and goes inside, he finds Columbo examining his appointment book. The detective notes that Lenore received a lot of lessons, When Columbo asks if he knew if Lenore had any affairs, Archer insists that he doesn't keep track of his clients' personal lives. Columbo asks him for a golf lesson and Archer reluctantly agrees. Out on the course, Columbo notes that 13 of Archer's lessons with Lenore were all the last lesson of the day. Archer stumbles through an explanation, and Columbo makes a perfect shot and tells him to get a lawyer.
Brimmer is meeting with his team on the Kennicutt investigation, and tells them to pursue the mugging angle. Columbo arrives with the files on the case, and Brimmer asks for a rundown. The lieutenant has nothing to report, but points out that according to the autopsy report, she was struck on the left check and thee was an odd cut. Columbo believes it was left by a ring, like the one on Brimmer's left hand. Since the cut was on the left cheek and it was an open-handed blow, the killer was left-handed. Columbo also believes that the murder wasn't premeditated, because most people don't kill with their bare hands, and that the killer has a temper. As he goes, Columbo has him sign a receipt for the files and notes that Brimmer is left-handed, just like the killer. Brimmer demonstrates that he's ambidextrous. As Columbo goes, he notes that Brimmer's car was tarnished by salt water, and figures he lives at the beach. Brimmer confirms that he does, and Columbo asks if he's ever been to Kennicutt's beach house. When Brimmer says he hasn't, Columbo comments on the coincidence and leaves.
That night at the country club, Archer packs his bags and leaves and finds Columbo waiting for him. The lieutenant suggests that they go for a walk. As they do, they're unaware that one of Brimmer's men, Wilcox, is watching them. As they walk, Archer admits that he had an affair with Lenore, just like Columbo suspects. He explains that Lenore became guilty, and believes that she really loved her husband. Archer figured that the police would find out about him. He admits that he doesn't have an alibi, but Columbo says that he's innocent because the killer had a ring and Archer doesn't have a ring, or a tan line indicating he wore one. The lieutenant asks if Lenore ever suspected her husband knew about the affair. Archer says that she did, but he was the one who spotted a man in a suit following them.
Wilcox calls Brimmer and reports that Columbo is meeting with Archer. Brimmer then calls a man, Leo Gentry, and has him set up something with Brimmer's secretary.
The next day, Brimmer's man Denning shows Columbo around the agency. He demonstrates a hidden metal detector and is surprised to discover that Columbo doesn't carry a gun. When he talks about how one of their clients came in with a gun, Brimmer overhears him and snaps. He invites Columbo into his office for lunch and then says that he's found two derelicts who were near the scene. Columbo tells Brimmer that Lenore was having an affair with Archer, and someone was watching them. He suggests that Kennicutt hired someone to check up on Lenore, and that person lied to Kennicutt and then tried to blackmail her. Brimmer warns that it's impossible to prove, but suggests that Columbo pursue it. He then offers Columbo a high-paying job with Brimmer Associates. Columbo wants to talk it over with his wife, and Brimmer sells the virtues of being in the private industry rather than the police. The lieutenant asks if he'd be working on the Kennicutt case, and Brimmer admits that he has more important matters to put him on right away.
As Columbo goes, he talks to Denning and apologizes for getting him into trouble with Brimmer. Denning says that Brimmer has a temper, and Columbo asks if anyone else makes as much as he might. The investigator says that their top-paid employee is Leo Gentry. Columbo describes the man that Archer described, and Denning confirms that it's the same man. He gets Leo's address from Denning and leaves.
Leo's wife Ceil returns to her child at the playground and finds Columbo playing with her son. He introduces himself and asks where Leo is, and she tells Columbo that her husband is on a special assignment. Ceil doesn't know when he'll be returning, but knows that he took his passport and figures that he's overseas. Columbo asks if Leo was on a case following a woman, and she admits that she and her husband don't discuss his business. She suggests that Columbo ask Brimmer, and Columbo notes that Brimmer probably won't be much help.
Later, Columbo goes to get his driver's license renewed and waits in line at the eye examine counter. The woman in front of him comments on her glasses, and Columbo remembers that Lenore wasn't wearing glasses.
Columbo goes to see Kennicutt and notes that a photo he saw earlier of her and Kennicutt showed her with glasses. However, there were no glasses on the body. Kennicutt explains that she switched to contact lenses shortly after the photo was taken, and she wore them all the time. The lenses aren't among her personal effects, and Columbo reluctantly asks for permission to exhume Lenore's body.
Later, Wilcox drives by the cemetery and calls to tell Brimmer that Kennicutt signed an exhumation order and they're preparing to remove her body from the vault. Brimmer goes to the parking garage to get his car and discovers that it won't start, even though there is no obvious problem. He arrives at the cemetery in another car and asks and Kennicutt what is going on. The publisher explains about how Lenore was wearing her contact lenses when she was murdered, and may have lost one or both of them at the scene of the crime. Brimmer dismisses it as a long shot, but Columbo notes that Lenore was struck hard and a lens could have been knocked out.
The medical examiner confirms that the right contact lens is missing. Brimmer suggests it could be a hundred different places, but Columbo says it could be at the place where Lenore was murdered. Kennicutt backs him and tells him to pursue his hunches. As the lieutenant leaves, Columbo says that he wishes the killer knew what they knew, since he might reveal himself to find the lens.
That night, Brimmer searches his beach house for the missing contact lens without success. Columbo arrives and eventually tells him that he can't accept Brimmer's job offer. He doesn't want to give up the Kennicutt case given he's so close to a solution, and assures Brimmer that when he solves it, Brimmer will be the first to know. Once he leaves, Brimmer goes back to searching the rug. He gets an idea and calls the repairman at his business to confirm that his car was taken in for repairs.
Later, Brimmer breaks into the garage and finds his car. He opens the trunk and searches for the contact lens, and finally finds it. As he gets out of the trunk, the lights come up. Columbo, Kennicutt, and the police officers are all there. Brimmer says that it's none of his business what he's doing, and Columbo points out that he'll need a good explanation for breaking into a garage. The investigator claims that he was looking for papers for an emergency case, and Kennicutt accuses him of murdering his wife. Columbo invites him to come downtown and Brimmer starts to walk off. As he tries to throw the contact lens away, Columbo has an officer grab his arm. Realizing that he's been caught, Brimmer tells Kennicutt that it was an accident. Columbo says that the cut on Lenore's check was the giveaway, and that when he read Brimmer's palm, he realized his ring matched the cuts.
As Brimmer is taken away, Columbo explains that when he talked to the medical examiner at the cemetery, the man confirmed that both contact lenses were on the body. The fact that the contact lens that Brimmer found isn't the real one doesn't matter, since he incriminated himself. Kennicutt asks what would have happened if Brimmer's car hadn’t broken down. In response, Columbo says that they would have found another way. He then comments about how as a youth, he used to stop cars by jamming potatoes in the exhaust pipes. Kennicutt starts to look at the exhaust pipe on Brimmer's car, and then leaves with Columbo.