Two years have passed since the events that rocked the Beverly Hills Police Department. Captain Andrew Bogomil is still leading the charge, while Detective Billy Rosewood and Sergeant John Taggart find themselves entangled in a series of sophisticated heists known as the Alphabet Crimes. Each crime scene is identified by a mysterious letter, leaving the investigators in a conundrum. Compounding the problem is the newly appointed, self-important Police Chief Harold Lutz, who unjustly suspends Bogomil for seeking aid from the FBI, claiming he is merely catering to the political ambitions of Mayor Ted Egan. This suspension leads to significant upheaval, as Rosewood and Taggart are demoted to mundane traffic duty, while Bogomil becomes a target for the ruthless henchwoman Karla Fry, who works under the cunning mastermind Maxwell Dent. In an unforeseen twist, Bogomil suffers a severe injury during a brutal ambush that leaves him with a cryptic message marked "B."
Elsewhere, news of Bogomil's attack reaches Detroit, where Detective Axel Foley learns about it through a television report. Seizing the opportunity, Foley sets out to investigate the brutal attack on Bogomil. His investigative instincts lead him to a local gun club, where he discovers key evidence linking bullet casings from the "A" jewelry heist to the club's manager, Charles Cain. Infuriated that his weapons are traceable back to the club, Dent instructs Cain to eliminate Foley.
Foley narrowly escapes an assassination attempt from Cain's henchmen yet manages to retrieve a valuable matchbook. Under the cloak of night, he breaks into the gun club, uncovering vital coordinates that set him, Rosewood, and Taggart on a thrilling chase to the city's deposits. Here, they successfully thwart both the "C" and "D" operations. In a desperate attempt to pursue the perpetrators in an armored car, they commandeer a cement mixer truck, leaving chaos in their path. Although they ultimately lose control of the vehicle, Axel, Rosewood, and Taggart manage to track the culprits to the Playboy Mansion for an electrifying showdown against Karla and Dent.
As Axel cracks the case wide open, he uncovers key information from Sidney Bernstein, Dent's accountant, who reveals that the devious crime lord, along with Karla, is planning to escape to Costa Rica. Meanwhile, Bogomil’s daughter Jan stumbles upon alarming information—Dent's enterprises are on the verge of financial collapse due to insurance issues, except for the thriving Empyrean Fields racetrack. Axel deftly interprets the cryptic "D" and realizes it is linked to Carlos, revealing that Dent intends to pin the Alphabet Crimes on Cain.
The day unfolds with Karla and her gang executing a daring heist at Empyrean Fields, leaving Cain seriously wounded. Lutz proudly claims the case is solved, but Axel’s sharp eyes catch a disturbing red mud trail near the stables, reminiscent of Bogomil’s running shoes. This new lead sends Axel, Taggart, and Rosewood racing toward Dent’s oil field, where they unveil a staggering truth: Dent has been funding his criminal operations with the $10 million he extorted to procure weapons from notorious arms dealer Nikos Thomopolis.
As the stakes skyrocket, Axel, Rosewood, and Taggart engage in a pulse-pounding shootout, successfully obliterating Dent's shipment trucks with explosives. However, Dent slips through their fingers, capitalizing on a moment of distraction. The climax reaches a fever pitch when Axel takes a precise shot that sends Dent's car tumbling down a hill in an explosive finale.
Just when it seems like the dust has settled, Karla appears, ready to finish Axel off, but Taggart is quick to intervene. With the remnants of Dent's gang cornered, police reinforcements arrive just in time to apprehend Thomopolis and his minions. Lutz and Mayor Egan join the fray, but Rosewood and Taggart confront Lutz about his incompetence and reveal Dent's true role as the mastermind behind the Alphabet Crimes aimed at financing his arms dealings.
The revelations prompt Mayor Egan to dismiss Lutz for his failure to effectively manage the investigation and for his treatment of the officers involved. Egan expresses his gratitude to Rosewood, Taggart, and Axel for their exceptional work in solving the case.
After recuperating from his injuries, Bogomil is named the new Police Chief, while Axel prepares to head back to Detroit. Mayor Egan takes a moment to thank Axel's superior, Inspector Todd, over the phone, but is met with a stern command to return to duty in Detroit.
