Four years after Isabel Aretas’ demise, MPD Detective Mike Lowrey weds his physical therapist, Christine. At their wedding reception, his partner, Detective Marcus Burnett, suffers a mild heart attack and has a vision of the late Captain Conrad Howard, who assures him it’s not his time to go.
Upon waking, Marcus feels invulnerable. Soon after, news surfaces linking Captain Howard to cartel corruption. Determined to clear Howard’s name, Mike and Marcus, with the help of Captain Rita Secada and mayoral candidate Adam Lockwood, start their investigation. They visit Mike’s son, Armando Aretas, in prison. Armando asserts Howard wasn’t corrupt but had knowledge of those who were, offering to help identify the real culprits.
When the conspirators try to hack Howard’s computer, a fail-safe video message is sent to Mike and Marcus, warning of extensive corruption in law enforcement. Using the code phrase “Coke bottle,” they find a QR code at their former hacker colleague Fletcher’s club, leading to another video from Howard. Assassins tail them to the club and kill Fletcher, while Armando fights off attackers in prison.
Mike, Marcus, and Armando are labeled fugitives after their helicopter crashes, following the conspirators’ murder of the pilot. U.S. Marshal Judy Howard, Conrad’s daughter, vows revenge on Armando. With support from AMMO members Dorn and Kelly, Mike and Marcus trace clues to uncover that DEA agent James McGrath, turned cartel associate, orchestrated Howard’s murder.
McGrath kidnaps Christine and Callie, Judy’s daughter, and sends men to assault Marcus’ family, but his Marine son-in-law, Reggie, defeats them. Rita, Dorn, and Kelly apprehend Lockwood, revealed as McGrath’s accomplice. Using Lockwood as bait, the team rescues Christine and Callie at an abandoned amusement park, where Lockwood is eaten by an alligator while attempting a double-cross.
McGrath takes Christine and Marcus hostage, forcing Mike to choose who will die. Mike shoots Marcus in his bulletproof vest, creating a distraction that allows them to break free. Mike then kills McGrath. Judy, thankful for Armando saving Callie, spares his life. The corruption is exposed, and Mike and Marcus are exonerated, celebrating with Reggie.