Professional photographer Paul Galesko (Dick Van Dyke) is seen in his photo studio creating a fake ransom note made from newspaper letter cut outs. It reads, "Mr. Galesko! We have your wife, do not call police, we will contact you," and we realize that Galesko plans on killing his wife Frances (Antoinette Bower), who is preparing to go to an auction that afternoon. A scene reveals that Galesko's marriage has not been a happy one, since she is very controlling. Galesko insists on taking her out to a ranch house he has recently purchased.
Galesko and his wife go out to the ranch house that afternoon. He takes his kit with him, in which he has his camera, and a clock. Once in the house, he sets the clock down on the fireplace mantle and sets it forward to 2:00 PM. Then he pulls out a rope from his briefcase and ties up Frances to a chair. As she demands to know what he is doing, Galesko takes two photographs of her, carefully positioned to show the time (to give himself an alibi). He coldly admits that he has had a "dream" where a man calls and regretfully informs him that his wife is dead, and he does not want to endure another day with her. As Frances pleads for Galesko to untie her, he pulls out a Walther P38 pistol and shoots her. After resetting the clock to the correct time, he leaves.
Galesko then stops at a filling station, on his way north to take some photos at a nearby lake, where he calls his assistant (JoAnna Cameron). Afterwards, he asks the attendant for the time, which is now two o'clock. At the lake, Galesko finds a man, Alvin Deschler (Don Gordon) waiting for him. It is revealed that Deschler is an ex-con who has been out of prison for three weeks, and Deschler assures Galesko that the ranch house and purchase is all in his name, revealing that Galesko is planning on framing Deschler for the murder. They leave, though Galesko tells Deschler to call him the next day at 10:00 AM from his motel room. Deschler mentions that someone broke into his motel room recently and stole the camera he bought, but Galesko assures him that it's no big deal - not mentioning that he has said camera.
The next morning, Galesko is at home and takes Deschler's call in the presence of his housekeeper. He makes it sound like he's talking to his wife's kidnapper, and arranges to meet with Deschler at a junkyard at 5:00 PM. He then hangs up on Deschler and pretends to be pleading to speak with the "kidnapper" before hanging up.
That afternoon, Galesko drives out to the motel where Deschler is staying. As soon as he leaves, Galesko enters his motel room and plants the newspapers he cut his fake ransom note's letters from, as well as the camera and other evidence that will point to Deschler. He then goes to the junkyard, where Deschler is already waiting for him. Galesko apologizes for his tardiness and shows the ransom note. Deschler is astonished, and he asks Galesko if he knows who is responsible. Galesko turns away, and apologetically informs Deschler that it will look like he did it. At that point, Galesko turns back around, pulls out a revolver, and shoots Deschler. He then pulls the P38 pistol he used to shoot Frances out of his briefcase, places it in Deschler's hand, and shoots himself in the right leg, to make it look like he killed Deschler in self-defense. As he staggers back to his car, Galesko runs into a drunken wino, Tom Dolan (Vitto Scotti), who asks if he is all right, and sees the bullet wound.
Columbo is brought to the scene. The sergeant on the scene mentions the cover story that Galesko has created and introduces Columbo to Dolan, the witness. Dolan, however, is obviously too drunk to speak, and they take him downtown to deliver his statement. Columbo interviews Galesko at the hospital, and Galesko mentions that he thinks his wife is probably dead if Deschler had the thought of mind to pull a gun on him. Columbo cannot help noticing powder burns around Galesko's bullet wound.
Frances's body is discovered the next day. Analyzing the scene, Columbo notices a discrepancy: the entire ranch house is dusty, but the clock has no dust on it, indicating that it was planted there. Furthermore, the man who sold Deschler the property, Calvin MacGruder (John Ashton), mentions that Deschler was always riding around in taxicabs. He also looked at a number of different properties, like he was unable to find a good purchase. Columbo determines that Deschler was purchasing the property for someone else.
Columbo also realizes something is up when he re-interviews Dolan, the witness. According to Dolan, who was sleeping in a junked car near the scene, he heard the first shot and thought someone was playing with a firecracker, but a short time later, he heard a second gunshot, yet Columbo remembers Galesko's statement as saying that the shots went off almost at the same time. When he confronts Galesko about this, Galesko claims that he and Deschler were standing less than a foot apart when Deschler pulled his weapon. He says the gun went off as he struggled for it, explaining the fact that the bullet wound was fired at point-blank range (creating the powder burns). Columbo also tells Galesko that the maid had cleaned the room the morning of Deschler's death and there had been no newspapers present in the room, indicating that they were placed there after the maid had been through there.
Columbo tracks down the camera shop that sold the camera found in Deschler's motel room. He learns that Deschler wanted a cheap camera, and claimed to the owner that he wanted to take pictures of houses. The owner also remembers that there was a cab waiting outside when Deschler purchased the camera.
Eventually, Columbo deduces that Deschler was taking cabs everywhere - something that would be very expensive to do so - because he did not have a driver's license. He reinterviews the driving instructor who administered Deschler's test, and learns that it was on the morning Frances Galesko was killed, which makes Columbo wonder why he would get his license the morning before he went to commit a kidnapping.
During a visit to Galesko's office, Columbo notices a book that contains photos from an excursion Galesko made to San Quentin Prison, documenting life there. He finds nine photos of Deschler in the album, proving that Galesko and Deschler have met and Galesko is lying about never meeting him before. Galesko is getting increasingly annoyed with Columbo following him around, but Columbo finds the evidence needed to incriminate Galesko.
To do so, Galesko is brought down to the station and showed the negative of one of his photos of Frances tied to the chair. He finds Columbo recreating the fake ransom note, and Columbo points out another discrepancy: he can't make the note without creating a huge mess, and points out that there would have been a lot of paper scraps all over the floor if Deschler had made the ransom note in his motel room. We can see that the photo shown is a reverse negative as the fireplace mantle and clock are on the right hand side of the photo when they were actually to the left in the original photo. Forgetting this fact, Columbo points out that the time on the clock is 10:00 AM. It means Deschler cannot have killed Galesko's wife as he had an alibi for that morning: he was taking his driving test at the time. Galesko points out that the photo is a reverse negative, and says the original must be still in the camera. He incriminates himself when he grabs a camera from the shelf. Columbo immediately points out that he grabbed the correct camera. Since Galesko identified it without asking, it proves that he could only have recognized it if he had used it to take the pictures.