Walter Prescott tries to extort all his wife Ruth's money to give her a divorce. As she leaves, a truck almost runs her down, instead crashing into a car and injuring the passenger. Ruth runs to a friend but returns to find Walter dead.
After Ruth Prescott's husband Walter refuses to give her the divorce she's asked for, she runs out of the house and is nearly run over by a furniture delivery truck that rams a parked car severely injuring the occupant. Ruth is convinced that her husband tried to have her killed to get his hands on what is left of her inheritance. She calls Jimmy McLain who she is in love with who tells her to come to his apartment. When she arrives, Jimmy is gone but his gun holster is there - empty. She returns home to destroy love letters from Jimmy McLain but finds her husband dead on the floor and a gun lying on the carpet beside him. While burning the love letters, Walter's secretary Margaret Swaine walks in and leaves after seeing the body. Ruth takes the gun and a toppled bird cage with an injured canary. She consults Perry Mason who puts Paul Drake on the case to track down the people involved. Paul finds the the car that was struck has been found with the driver dead. Ruth is charged with her husband's murder and it's up to Perry to sort out just what happened.
- Ruth Prescott (Stacy Graham) wants a divorce, but husband Walter (William Kendis) threatens to create a scandal - he knows she's in love with Jimmy McLain (Biff Elliot). He'll only let her go in exchange for the $40,000 that remains of her personal fortune. Ruth refuses, and Walter reminds her that the marriage is "'till death do us part". Once she leaves the house, Prescott goes to the window and opens and shuts the blinds. Harry Jonson (James Philbrook) sees this from his transfer company van, and Frederick Walden (John Matthews) is also watching from his car. As Ruth crosses the street, the van speeds toward her. She stands frozen, screaming, until the last second, when she runs off. The van crashes into Walden's car. He's unconscious, although Harry is unhurt. Some people run up to the accident scene, including Prescott, who whispers "You bungled it" to Harry and tells him they need to get Walden out of there.
Ruth calls Jimmy and tells him that her husband tried to have her killed, and agrees to come to his place. Once they hang up, Jimmy takes his gun and writes a note. When Ruth arrives, she finds the note on the door, telling her he had to leave and the door is unlocked. She goes in and sees Jimmy's empty shoulder holster. She takes a cab home and inside her house she sees the birdcage knocked to the floor, with her pet canary still inside. Then she notices Walter dead on the floor, with a gun next to him. She puts the gun in her purse, then takes keys from the corpse, uses them to remove a packet of letters from a locked drawer, and returns the keys. She is in the process of burning the letters when Margaret Swaine (Susan Cummings), secretary at Prescott's office, enters. She says she had an appointment with Prescott to take some dictation, then sees the body. She asks if Ruth has called the police, then leaves. At the office of Prescott & Wray, insurance brokers, she calls to have her trunks and hand luggage picked up at one apartment and delivered to another. As she is going through the papers on Prescott's desk, his partner Ernest Wray (Berry Kroeger) enters. Margaret tells him of the murder and says she's looking for papers that the police might misunderstand.
Ruth goes to see Perry, bringing the canary along because she's afraid to leave him alone - something's been wrong with his foot since the cage was knocked over. She tells her story, omitting the gun at the scene and the letters she burned. Meanwhile, Lt. Tragg and Dr. Hoxie (Michael Fox) are at the murder scene. Hoxie says Prescott's been dead 1 or 2 hours. Tragg wants to know more about the scratches and bruises on Prescott's face, but Hoxie doesn't have anything specific. Sgt. Brice (Lee Miller) finds ashes in the fireplace and Tragg tells him to see what the crime lab can do with them.
Perry and Ruth visit Jimmy, who says that he went to see Prescott, who wasn't at home. He stayed at most ten minutes, while he found Ruth's suitcase and packed it with things she'd need. He tells Perry he has a gun, but it's in his car. He and Ruth both assume she'll stay there, but Perry says she must go to a motel and register under her own name.
Perry and Paul visit Harry, who says the accident was caused by a cut brake line, possibly the act of a competitor. He remembers Prescott as one of the people who came to the scene of the accident - he made note of the names while because he wanted witnesses. Harry says he personally took Walden to a nearby private hospital, and paid a young man to follow in Walden's damaged but drivable car. Lt. Tragg arrives as Harry continues, saying after leaving Walden at the hospital he returned to the accident scene to look for more witnesses. Prescott came out, asked him how Walden was doing, and went back in his house. Tragg asks Perry where Ruth is. He knows about Ruth burning envelopes and has a warrant for her arrest for murder.
At the Prescott and Wray office, Ernest tells Perry that Prescott had taken the company books home. Each partner was insured for $75,000, which in the case of the death of a partner, their widows were obliged by the partnership agreement to accept in lieu of a share of the partnership. Perry then sees Ruth in jail, and his miffed that she stayed with Jimmy, ignoring his instructions and giving a suspicious appearance when the police found her there. Even worse, the police found the murder gun in her purse. She says she never heard of Harry Jonson or Frederick Walden, but her husband had indeed brought company books home. Perry tells her to answer no questions without his permission. Later, Perry is at an accident scene on a treacherous road. Walden's car has been in an accident again, this time killing him. Paul brings Dr. Fowler (Emerson Treacy), who supposedly treated Walden after the first accident, but the doctor insists he never saw the dead man before.
In court, Tragg testifies that the murder weapon, found on Ruth, was registered to Walter Prescott. He identifies some reconstructions of the love letters that the crime lab has produced from the ashes. Margaret testifies that she arrived at the murder scene at almost exactly 2:30. She knows the time because that was the latest at which she was due to take dictation, and she barely made it in time. On cross-examination, Perry asks her is Prescott ever visited her, not at her regular apartment, but at the more expensive place she rented under the name Maxine Starrett. She says that's part of her personal life and she won't discuss that or the baggage she had transferred there. She does state outright that she wasn't seeing Prescott. Jimmy testifies that he did write the love letters to Ruth, but only before she was married. Burger claims it's still suspicious that she held on to love letters from another man throughout her marriage. (Apparently, no one remembered that it was Prescott who was holding them.)
During a recess, Paul says that Margaret is leaving town and with Ernest's help has arranged for a truck to pick up the baggage at her expensive apartment. He finds this suspicious, but Tragg isn't interested. Paul adds that Prescott's bank balance was over $100,000. Also, Walden was an investigator for the Board of Fire Underwriters. Perry tells Della to buy a couple trunks and some luggage, have it all monogrammed "M.S.", and have it delivered to "Maxine's" apartment. After the delivery, Perry and Della visit the apartment manager (Chet Stratton), claiming Della's baggage was delivered there by mistake. The police have been notified, and Lt. Tragg arrives. In the apartment, Della explains that her bags were monogrammed M.S. because the store misunderstood when she said she was Miss Street. She gives permission for her baggage to be opened, to determine which are hers. Tragg clearly doesn't believe a word of this, but goes along and begins by having one trunk opened. It's full of fur coats.
Back in court, Ernest testifies that Ruth could have gained $75,000 from her husband's demise. On cross, Perry makes him admit that, due to the partnership agreement, the death actually cost her a share of a business now worth $250,000. Ernest also testifies that his firm brokered a policy for a furrier that subsequently suffered a $108,000 loss in a fire. Perry then recalls Margaret, who pleads the Fifth when Perry asks about her role in insurance fraud. He then recalls Harry and suggests that he aimed his truck not at Ruth but at Walden. It was Prescott who drove Walden's car to the hospital. Harry hit Prescott to make him look injured, and Prescott saw Dr. Fowler, posing as Walden. Then they drove to the canyon road and pushed the car down a ravine with Walden in it. Later, he got into an argument with Prescott and killed him. Harry admits it - after all the risks he was taking, Prescott expected him to be satisfied with $10,000. Perry asks if being guilty of two murders satisfies him.
Later, Perry, Della, and Paul are in the office with Ruth and the canary, who seems much more active now. Burger and Tragg join them. They discuss the fact that Margaret was in on the insurance fraud with Harry from the beginning, although not involved in the murders. Perry says that thinking about the canary's cage being knocked over got him thinking about Prescott being killed in a fight. Burger says it's the first time he heard of a lame canary turning out to be a stool pigeon. Everyone laughs.