In Las Vegas, Glenn Faulkner is losing at the craps table when a model comes over and bets against him. Faulkner misses his point and leaves, tapped out, while the model collects her bet. As Faulkner leaves the casino, a man watches him go. Back at the hotel he owns, Faulkner writes a letter to his daughter Stephanie, admitting that he lost his money gambling. The man from the casino, George Castle, comes in and demands the $8,000 that Faulkner owes him. The note is payable on demand and Castle wants it now. Faulkner figures that Castle wants the land so the mob can put up a new casino, and Castle admits that he put up $50,000 as a guarantee. He assures Faulkner that he's selling but the hotelier promises to keep the land for his daughter Stephanie. Once he's sure that Faulkner won't deal, Castle takes out a gun and shoots Faulkner dead.
Later, Castle goes to see Stephanie in Los Angeles and shows her Faulkner's promissory note. He tells her that he can sell the hotel land to cover the note but he has to do it within 24 hours, but Stephanie tells him that she's not selling. Castle warns her that the people he can sell the land to need it within two days and asks if she's going to discuss it with Mike Garvin Jr., a used car salesman and her friend. He tells Stephanie that she can find him at the Lodestar Apartments. Once he leaves, Stephanie makes a phone call.
Soon, Mike goes to see Castle at his apartment. Castle is expecting him and points out that Mike went to Vegas to marry a long-legged model named Margo Davis. The racketeer warns Mike that just because he used to be engaged to Stephanie doesn't mean he can butt into his business. Mike doesn't see it that way and Castle warns him that Mike Sr. might get mad if he knew his son was involved because he has a thing for Stephanie himself. Mike throws a punch at Castle, who easily blocks it and punches Mike in the gut. He then shoves Mike out and tells him to go home to his bride.
Castle goes to Mike Sr.'s investment office and greets the receptionist, Eva Elliott. He sits her down and accuses her of double-crossing him after he got her the job at the office. Castle figures she tipped off Mike about his offer to Stephanie, but Eva insists that she had nothing to do with it. The racketeer reminds her that the law in Kansas is still looking for her on a check-forgery charge. The phone rings and Castle hands the phone to her. It's Stephanie, who asks to speak to Mike Sr. Eva says that her boss is out of town and carefully avoids mentioning Stephanie's name where Castle can hear it. Once she hangs up, Castle tells Eva to keep her nose clean and takes off. Once he goes, Eva calls Stephanie back and tells her that Michael is in Las Vegas and flying back late that night, and will meet Stephanie at Perry Mason's office the next morning. The secretary is unaware that Castle has come back and is listening in. Once she hangs up, Eva sees Castle, who says he's going to call the sheriff in Kansas and walks away.
The next morning, Stephanie and Michael meet at Perry's office. Stephanie explains that she contacted Michael after Castle contacted her about her father's promissory note. Michael says that Castle's offer is only half the value of the land and that he suspects Castle killed Faulkner. When Perry points out he has no proof, Michael takes out a gun and assures the attorney that he's a deputy and has a license to carry, and that he owns three guns. Perry tells him to turn his information over to the authorities in Las Vegas and let them handle it. Stephanie breaks into tears, insisting that her father never let her down even though he was a compulsive gambler. Michael hugs her and leads her out, and Della figures that he's in love with Stephanie.
That night, Perry goes to Lodestar Apartments to see Castle. Castle admits that he lowballed his offer to make a profit and Perry says he'll need an offer of at least $225,000, $1,500 a front foot, to take to Stephanie, with no guarantee that she'll accept. They negotiate and Castle reluctantly offers $1,200. Perry dickers him up to $1,400 and a nervous Castle agrees, but Perry says he won't recommend Stephanie take less than $1,500. Castle refuses and Perry figures that he stands to take a big loss if he can't deliver the property. As he goes, Perry asks Castle how well he knew Faulkner. The phone rings and Castle tells the caller that he'll be there in ten minutes. The racketeer then tells Perry he'll pay the $1,500, and Perry tells him to be at his office in the morning.
As Perry goes outside, he walks over to a phone booth and calls Paul. He has the detective run a background check on Castle but then pauses when he sees Stephanie arrive in a taxi and go up to Castle's room. Perry then tells him that Faulkner was murdered and might be connected to Castle. Once he hangs up, Perry watches the apartment and sees a police car pull up. As they go up the front stairs, Stephanie comes down the back and Perry drives over to pick her up. Shocked, Stephanie gets in the car with him and Perry drives back out front. Tragg is waiting for him and they chat briefly. Perry says that he's taking Stephanie home without saying her name and Stephanie remains quiet when Tragg tries to get her to say her name. He's called up to the apartment and Perry figures that Castle is dead. Stephanie refuses to discuss it and asks Perry to take her home.
The next morning, Margo drives to Mike's used car lot to see her husband. They kiss and she points out that it's the first time she's been there, and Margo hands him his father's gun. She says that he must have been upset because he left it on the dresser, and Mike hastily puts it away and snaps at her. He then apologizes, saying he was concerned for her safety, and walks her back to her car.
At his office, Perry receives a call from Michael. He asks the attorney to take on Stephanie as a client, assuring Perry that he'll disregard any conflict of interest with Perry's work with him. Perry agrees and goes to see Stephanie. She insists that she didn't call Castle but admits that she had a gun with her. Stephanie assures Perry that she's never used it but Perry smells gunpowder and points out that one shot has been fired. She explains that Michael gave it to her the previous day after they left Perry's office. Perry asks why she went to Castle's office and Stephanie says that she hoped to question Castle and find out if he was involved with her father's murder. When she got there, Castle was already dead. Perry takes the gun and tells her not to leave her apartment or talk to anyone until he gets back.
Next, Perry goes to the used car lot to talk to Mike. He asks to see Mike's gun and then "accidentally" fires a shot into the desk. When Mike figures that Perry is up to something, the attorney gives the gun back and tells Mike to come with him. They drive to Stephanie's apartment and she offers Mike congratulations on her wedding. Perry quickly ushers Mike in and tells him to give Stephanie the gun. Perry tells her to tell the truth if anyone asked: Mike gave her the gun, one shot has been fired, and she has no idea who fired it or where. As Mike worries that Perry could involve Michael, the front desk calls to tell her that Tragg is coming up. Perry and Mike slip out the back.
Later, Perry and Della are having lunch at an outdoor restaurant when Tragg shows up. He explains that they book Stephanie on a solid case of murder. Perry is surprised to learn that Ballistics has confirmed that Mike's gun is the murder weapon. Tragg passes on Stephanie's message to have Perry come and see her and goes on his way.
At the office that night, Perry blames himself for giving Stephanie the gun. He figures Burger won't believe that he got the gun from Mike. Perry tries to call Mike at his office again. Margo answers and Mike refuses to take the call. Once she hangs up, Margo warns Mike that he'll have to talk to Perry eventually, particularly if he's subpoenaed for the trial.
The trial begins and Tragg testifies that he arrived at Castle's apartment at 8:30 and saw Stephanie in the vicinity. Burger has him confirm that the gun Tragg found in the apartment is the murder weapon. Stephanie told the lieutenant that Mike Garvin gave it to him. On cross-exam, Perry has Tragg confirm that Stephanie didn't say whether it was Mike Junior or Senior that gave her the gun or when. Burger then calls Eva Elliott to confirm the time element. She testifies that Michael came to the office at 5:30 p.m. after returning from Vegas. Perry objects to the testimony as immaterial but the judge overrules on the condition that he'll strike it if Burger doesn't connect up the time. Eva testifies that at 8 p.m. Michael did not have his gun in his shoulder holster. Perry declines to cross-exam.
Burger calls Michael to the stand and asks him to confirm if the murder weapon is the gun he gave Stephanie. Michael admits that all three of his guns look the same and he can only tell them apart by the serial numbers. Burger differentiates the three guns as the vault gun, the junior gun, and the holster gun. Michael testifies that he gave the holster gun to Stephanie and returned to his office. As Burger tries to unravel the timeline, the judge asks if Perry wants to object. Perry admits that he does but that he also wants to figure out the situation. Burger proceeds and has Michael confirm that he put the vault gun in his holster, and then took Stephanie to dinner. However, she refused, saying she had gone to Castle's apartment. Perry objects when Burger asks Michael to speculate if she took the holster gun with her. Burger withdraws the question. On cross-exam, Perry has Michael testify that he gave the gun to Stephanie because she was once engaged to Mike and after Mike married Margo, he wanted to make sure Stephanie was protected.
The court calls for a lunch recess. Back at the office, Perry talks to Paul, who admits that he never did find out where Castle got his money. He did find out that Castle owned a 40% interest in an expensive woman's shop in Vegas. Paul tells Michael that Eva and Margo both used to model there, but Michael insist that he didn't know. Michael takes offense but Perry confirms that Michael still wants him to defend Stephanie even if it hurts another member of his family.
Back in court, Perry wants to put Michael back on the stand. Burger objects since he has Mike ready to testify. Perry agrees to let Mike testify first and Mike states that Perry fired his gun into the desk and then gave him a different gun. At that, Perry objects, pointing out that it calls for a conclusion. Mike insists that Perry must have switched the guns because it turned out to be the murder weapon and he knows it wasn't his gun. The judge sustains the objection and Burger has Mike testify to the identity of the junior gun, the one that Perry fired. Mike shows them the initials he scratched into the handle. He then testifies that he took a gun to Stephanie's apartment and stood there while Perry gave Stephanie the weapon. Burger is happy to point out that Perry tried to contaminate the chain of evidence until Perry objects. The judge sustains the objection and warns Burger to stick to questions.
Perry cross-exams Mike and has him confirm that he took the junior gun home with him and put it on the dresser when he went to bed. The next morning, Mike admits that he left the gun behind and Margo brought it to the office later. Perry asks if Margo may have used the gun that night and Mike snaps at him. Burger objects to the insinuation but the judge overrules him and then suggests that he confirm if the bullet at the used car lot was fired from the murder weapon. The district attorney admits that the bullet ricocheted off the desk and out the window, and they were unable to find it. Perry starts to question Mike again but then declines.
Burger calls Margo to the stand and shows her the murder weapon. She testifies that she saw a similar gun on Mike's dresser on the night of the murder, and again the next morning. Margo then took it to Mike. On cross-exam, Perry has Margo confirm that she knew Castle as the owner of the shop where she modeled, but she didn't have a personal relationship with him. She testifies that she stayed at home on the night of the murder and Perry ends the questioning. Perry asks to confer with his client before calling Michael back to the stand and the judge orders a recess.
Once they're alone, Perry tells Stephanie that she lied to him and asks how she really feels about Michael. He suggests that she might have feelings for him like for her own father. When Stephanie doesn't see the point, Perry says that it could answer the issue over the guns.
When the court returns from recess, Perry questions Michael and points out that the time may have come when he has to sacrifice Michael to save Stephanie. Michael testifies that he gave Stephanie the holster gun and then that night put the vault gun in his holster. Realizing the truth, Perry has Michael confirm that he switched the vault gun for the holster gun without Stephanie's knowledge. He reluctantly explains that he thought she killed Castle in self-defense so he switched guns to protect her. That raises the question of how the vault gun was used to commit the murder. Michael insists that he didn't kill Castle and that the only other person with the combination is Eva. Michael's office is only two blocks from the Lodestar and it took him 30 minutes to shower and shave before taking Stephanie to dinner at 9. Eva was in his office working late and Perry, satisfied, ends his questioning.
Before Burger can call her to the stand, Eva steps forward and apologizes to Stephanie. She admits that she never intended to frame her, and was just trying to make something of herself until Castle stopped her.
Later, Perry and Della visit Mike and Margo at Mike's office. They explain that Stephanie hid the gun that Mike and Perry gave to her because she thought Michael had used it to kill Castle. Mike tells them that Michael and Stephanie are at City Hall getting married and gives Perry a blank check for services rendered. He offers to take Della for a test drive and Margo protectively takes his arm and insists on going with him.