Mitch shoots Vargas with a gun concealed inside Julio's camera. Showtime gets a second season, this time with two female cops. Trey passes his detective's exam, and he and Mitch are partners and getting along better.
Mitch Preston (Robert DeNiro) is a LA police detective investigating a supergun. While undercover with his partner, his cover is blown by patrolman Trey Sellars (Eddie Murphy), who attempts to arrest Mitch. Mitch gets the drop on Trey and handcuffs him to a fence and gives chase to the bad guys, all caught on camera by a news helicopter. During the chase, Mitch's partner is killed, and the bad guys get away. Afterward, a news cameraman gets in Mitch's way, so Mitch shoots the camera. The network that employed the cameraman sues the LAPD, but they will drop the lawsuit only if Mitch agrees to star in their new reality TV program. He refuses, but his chief orders him to participate.
Meanwhile, Trey, who is also a part-time actor, hears about the show and wants to be a part of it. He pays a friend to snatch the purse of the show's producer Chase Renzi (Rene Russo), then Trey shows up and arrests the criminal. Mitch, who was having lunch with Chase at the time, quickly sees that the scene was staged, but Chase is impressed with Trey and hires him to be Mitch's partner, much to his dismay. Trey also comes up with the title of the program, Showtime. In order to act like TV cops, Chase hires William Shatner (playing himself) to come in and show Mitch and Trey how to act like his old TV character TJ Hooker. Trey is taking it all in, but Mitch is just annoyed because he says a real cop would never do anything TJ Hooker routinely did.
Despite the constant presence of Julio (Judah Friedlander), the show's cameraman, Mitch continues his investigation of the supergun. He is able to trace the owner of the gun to arms dealer Caeser Vargas. Mitch and Trey track down Vargas at his nightclub, and get into a fight with his henchmen, all while wearing hidden cameras. The bonding experience puts Mitch in a good mood and he and Trey are able to have a friendly conversation. The next day, Mitch and Trey, along with the show's producers in a TV truck, arrive at the scene of a robbery of a armored truck. The robbery is being pulled off by Vargas and his men are using several superguns. Mitch and Trey chase the robbers and get in a shootout, but it ends with the destruction of a construction site and the bad guys getting away.
As a result of the chase gone spectacularly wrong, the chief cancels Showtime. While watching the last episode, Mitch sees his CSI friend Charlie at the nightclub the night of the fight. He calls Trey, who was also watching the show, and they go to Charlie's house. They find his workstation where he built the superguns, and also find out he will be selling them at a gun show inside the Bonaventure Hotel. They go there the next day, along with Chase and the TV crew. They quickly find Charlie and Vargas, who begins a shootout in the gun show, where Charlie is killed. Mitch and Trey pursue Vargas, who has taken Chase hostage, to his penthouse suite. Vargas demands that they come in and tape his demands for his escape and the release of Chase. Before they can go in, Julio stops them to say he needs to replace his tape. This gives Mitch an idea.
Mitch takes Julio's camera and places a small gun in the tape holder, then he and Trey enter the room. With Vargas holding a supergun on Chase, Mitch points the camera at Vargas, then shoots him with the hidden gun. As Vargas is falling backward from being shot, he fires the supergun several times, punching holes into the ceiling and into the swimming pool directly above them. This causes the suite to quickly fill with water, which washes Vargas out the window to his death. After getting Chase out of the room, Mitch and Trey are also about to be washed out, but Trey handcuffs himself to Mitch and grabs the window ledge, saving both of their lives.
With the case closed, the chief reconsiders and allows Showtime to continue production. However, Mitch and Trey will not be allowed to continue to work on the show. Chase quickly hires two female cops to be the new leads for the second season. The movie ends with Chase kissing Mitch, hinting at a budding relationship between the two. Mitch and Trey, who had just passed his detective's exam and is Mitch's new partner, are getting along much better, and the two begin to investigate another case together.