Bitter because his rich wife Lois is going to divorce him, Howard Frazer buys a revolver and concocts an elaborate scheme to murder her and make her death appear to be the work of a burglar. After Howard leaves home early for the airport for a trip to Seattle, Lois discovers his purchase and telephones her boyfriend, homicide lieutenant Ed Cullen. Instead of Ed, however, the phone is answered by his younger brother Andy, who has just joined the homicide bureau. When Andy tells Ed that a woman called for him and then hung up, Ed guesses that it was Lois and goes to her house. As they are discussing Howard, he sneaks back into the house, but Lois, who has already retrieved the revolver from its hiding place, panics upon recognizing him and shoots him. Blinded by his love for Lois, Ed decides to hide her crime, which could be prosecuted as murder, by making Howard's planned alibi work for them. To make it look as though Howard was robbed and killed at the airport while awaiting his flight, Ed dumps Howard's body at the airport parking lot, but is seen by an elderly couple, Ernest and Muriel Quimby. By the time Ed reaches the Golden Gate Bridge, Howard's body has been found and a road block has been set up to trap the green coupe described by the Quimbys. Ed is stopped by Patrolman Blair, but because his coupe is blue, he is allowed to pass. Ed stops on the bridge and throws the revolver into the water, and later, returns to the airport to help Andy, who has been put in charge of the case, his first. The Quimbys reveal that they did not get a good enough look at the driver to identify him, and the cool, collected Ed accompanies Andy to Lois' home, where she pretends not to know him. Lois feigns distress at the news of Howard's death, and Andy and Ed then return to their apartment, where Andy ponders why Howard arrived at the airport parking lot in the early evening, even though his flight was not until midnight. Ed dismisses Andy's qualms by asserting that the case is a botched robbery, but Andy continues to worry. Soon after, Andy marries his fiancée Janet, but delays their honeymoon to finish the case. Just after the wedding, Andy is stopped for a traffic violation by Blair, who mentions that he saw Ed on the bridge shortly after Howard's body was found. Later, the owner of a liquor store is robbed and shot, and ballistics expert Rushton informs Ed and Andy that the same gun that killed Howard was used in this incident. Ed is flabbergasted by the latest development, which he relates to Lois. She asks him to marry her and promises to support him, but Ed declines, commenting that she changes her mind too easily to love one man for long. The gun involved in the liquor store shooting is later pawned by Mrs. Capa, who, when questioned by Ed and Andy, asserts that her husband Pietro found it on his boat. While Ed realizes that the gun landed on Capa's boat when he threw it from the bridge, he and Andy apprehend the Capas' son Nito, who, although he committed the robbery before his mother pawned the gun, denies any involvement in Howard's death. Later, Ed is visiting Lois when Andy drives by and sees Lois in the window before Ed exits the house. Andy is puzzled by Ed's lie that Lois is sedated and in bed, but does not say anything. The next morning, Andy reads a newspaper story about the Golden Gate Bridge and realizes that Ed was on the bridge at the same time that the revolver was thrown into Capa's boat. Fearing that Ed is involved, Andy borrows his car to show it to Quimby and when Quimby identifies it as the car at the airport, realizes that Quimby is color-blind. Ed deduces that Andy is closing in on him and rushes home, but Andy is there waiting for him. Ed confesses that he covered up Howard's murder because of Lois, then knocks Andy out and ties him up before leaving to pick up Lois. When Janet calls Ed's apartment in search of Andy, Andy manages to alert her to his situation, and soon, an all-points bulletin is issued for Ed and Lois. Ed decides to hide in the deserted Fort Point, where he and Andy played as children. Andy deduces where Ed and Lois are hiding, however, and they are captured that evening. Soon after, Ed reacts stoically when he encounters Lois in the courthouse and overhears her flirting with her lawyer.