When an undercover detective is shot dead while investigating a string of Porsche 911 thefts, Lieutenant Vincent Bracey assigns 22-year-old San Diego officer Benjamin “Benjy” Taylor to infiltrate a Porsche garage suspected to be a front for the grand theft auto scheme. Benjy is chosen because of his extensive mechanical knowledge of German cars and his rookie status, which dissuades others from suspecting that he is a cop. Bracey wants Benjy to obtain evidence that millionaire playboy Ted Varrick is the mastermind behind the thefts and the murder of the detective.
Using the alias “Billy Ayles”, Benjy moves to Los Angeles and gets a job at Technique Porsche as a mechanic. After Benjy fixes Ted’s Porsche one night, the two men become close friends, and Benjy becomes romantically attached to Ted’s sister Ann. Benjy also discovers the presence of a rival syndicate led by Frank Martin, which leads him to believe that Ted is not the prime suspect despite Bracey’s insistence.
Eventually, Ted brings Benjy into his side business of stealing Porsches, with garage manager Malcolm coordinating the operations. Benjy’s first few attempts at stealing cars fail miserably, with Frank’s syndicate catching on and slashing his hand as a warning. While doing a job at the mall, Benjy and Ted are confronted by Frank and his thugs, but they manage to lose them in a lengthy car chase. Ted rewards Benjy with a red Porsche that night. The next day, Ted goes to Technique Porsche and finds Malcolm has been murdered. In retaliation, he kills Frank at a night club.
During a phone conversation at a party, corrupt police Lieutenant Curtis Loos – who was hired by Ted to take out the detective in the film’s opening – tells Ted about Benjy’s real identity. The next night, Ted has Benjy meet Loos at a warehouse for a payoff. When Loos tries to kill Benjy, Ted runs him over to save his friend in spite of what he knows. Later, Benjy stops at Bracey’s house to inform him of what happened with Loos, and accuses the Lieutenant of conspiring with him. Bracey kicks Benjy out, but tells him to call in the morning so they can work things out. Benji drives off, unaware that Ted is nearby, spying on him.
The next day, Benjy’s cover is blown in front of Ann when his uncle Mike pays him a visit at his apartment. He goes to Bracey’s house, only to find that Ted has murdered him. Ted is preparing to flee the country when Benjy convinces him to meet up at the mall, where he tries to arrest Ted for the murders. Ted refuses to go quietly and a gunfight breaks out; Benjy is wounded, but manages to shoot and kill Ted.