At a surprise birthday party organized by Dale Hyde at Britt Reid's house, Britt is given a .45 handgun as a gift from everyone at the Daily Sentinel. Turning around to give thanks, Britt is stunned to see Eddie Rech in attendance. Hyde says that the two have been enemies long enough and that they should shake hands. Britt refuses and turns away, but Rech advances toward him and says that Britt has made a fool of him for the last time. Britt turns around to face Rech and the gun goes off, killing Rech with a single shot.
Moments later, after all the party guests/witnesses have left, D.A. Scanlon questions why Britt would do such a thing. Britt protests and says that gun went off on its own. Scanlon doesn't believe him and reminds Britt of the witnesses and public knowledge of the feud between Britt and Rech. Britt says he did have bad blood toward Rech for messing with the Sentinel's circulation, but that he would never kill a man in cold blood. Britt says that only one person can prove his innocence now: The Green Hornet. Scanlon tries to stop Britt and calls for one of the police officers outside. Britt knocks Scanlon out and shorts out the lights by sticking an ice pick in an electrical outlet. A police officer comes in and gives chase, but Britt escapes through the hidden fireplace elevator. In the Black Beauty, Kato tells him that he has just made it worse and reminds him that he can't go to police headquarters to examine the gun. Britt tells him that the Green Hornet can.
At the police station, Green Hornet and Kato subdue the officers on duty and Green Hornet examines the gun that killed Eddie Rech. He finishes just as two policemen break into the storeroom where the gun was. Green Hornet knocks them out with Hornet Gas and he and Kato escape the police station.
Meanwhile, Casey is protesting an article by interim publisher Dale Hyde that will surely result in a conviction for Britt. Hyde tells her that she isn't thinking clearly because of her feelings for Britt. Casey begs him to bury the article. Hyde says he will tone it down.
In the Black Beauty, Green Hornet tells Kato that the gun's mechanism worked, but that it felt lighter than before. He asks Kato if he saw a clip in the gun, but Kato didn't. Kato then reminds Green Hornet that Dale Hyde took the gun from him after Rech was shot. Green Hornet remembers that Hyde gave him the gun in the first place. At the Daily Sentinel, Hyde dictates a story about Britt for the paper as Britt walks in. Britt asks Hyde where he got the gun and if anyone could have tampered with it. Hyde tells Britt to give himself up and let the paper fight for his innocence, but Britt refuses. As he leaves, he asks Hyde to call the police and find out if a clip was picked up with the gun. He tells Hyde where he'll be hiding and when to come see him with the information. After Britt leaves, Hyde dials the police and anonymously tells them where Britt will be hiding. He also says that Britt will be armed and dangerous.
Later, Kato drops Britt off at the warehouse where he'll meet with Dale Hyde. Kato protests that Britt might be walking into a trap, but Britt says it is the only way to prove whether or not Hyde is behind Eddie Rech's murder. Moments after arriving, the police show up and chase Britt through the warehouse. Britt escapes and is picked up by Kato. They now know Dale Hyde is behind this scheme, but they need to prove it. Britt says they need someone who likely saw everything and tells Kato to drive to Casey's apartment.
After picking Casey up, Britt tells her to recall everything she saw at the party. She tells him about how Dale Hyde turned away after taking the gun from him. Then Hyde gave the gun to Scanlon. As Casey went upstairs for a first aid kit, in case Rech wasn't really dead, she saw Hyde put something in the flowerpot on the bar. After returning to his house with Kato and Casey, Britt finds the clip from the gun, but it isn't a normal clip. It's filled with electronics. Britt says he needs one more thing and he'll give himself up to the police at his house the next morning.
The next morning, Britt has gathered Casey, Scanlon, Mike Axford, Dale Hyde, and a police officer to reenact the crime. After placing the clip in the gun and positioning it on the table, Britt tells Hyde to walk towards him. Before he does, Britt gives Hyde the same transistor radio that Hyde had given Rech at the party. Hyde then refuses to walk forward. Britt confronts him with the fact that the radio sets off the gun when it comes within a certain distance and proves this by walking toward the gun with radio in hand. However, this time the gun discharges a blank shell. Hyde then pulls out another gun and attempts to take Casey hostage, but Britt rolls and knocks him out before he can escape.
After Hyde is taken away, Britt tells Mike, Casey and Scanlon that Hyde presented the facts by trying to convict the accused in newsprint and tells Mike to write the story. Casey says she thought she was on her way to Brazil with Hyde, to which Britt remarks that she has wanted a vacation. Casey asks him for one and he jokingly tells her to take a whole hour for lunch.