Plot

Miami detectives Mike Lowrey and Marcus Burnett must face off against a mother-and-son pair of drug lords who wreak vengeful havoc on their city.

Marcus and Mike have to confront new issues (career changes and midlife crises), as they join the newly created elite team AMMO of the Miami police department to take down the ruthless Armando Armas, the vicious leader of a Miami drug cartel.

It is seventeen years after Johnny Tapia was taken down by Miami PD Detectives Mike Lowrey and Marcus Burnett.

Isabel Aretas (Kate Del Castillo), widow of cartel kingpin Benito, escapes from a Mexican prison with the aid of her son Armando (Jacob Scipio). Isabel kills a female guard inside the prison, and with the help of the other female prisoners, she changes into her clothes. The prison security arrives and takes the female guard for medical assistance in an ambulance. Unknown to them, they were taking Isabel out of the prison. Outside the prison, Armando had set up a blockade and attacks the ambulance to free up Isabel. Inside the prison, the body of the dead prison guard is discovered inside a laundry machine.

Isabel sends Armando to Miami, tasking him with recovering a substantial stash of money his father Benito had hidden, as well as assassinating the people responsible for his father's arrest and eventual death in prison. Isabel demands that Armando kill Miami Detective Lieutenant Michael Eugene 'Mike' Lowrey (Will Smith) last. Isabel gives Armando a flash drive with the current locations and identities of the people responsible for the death of her husband. Armando starts by deposing off the local crime lords and taking control of the local drug operations in Mexico City.

In Miami, Mike accompanies his partner Detective Lieutenant Marcus Miles Burnett (Martin Lawrence) to the birth of his first grandson. Mike tears through the town in his brand new Porsche, with a police escort, even as Marcus is almost sick and on the verge of vomiting. Marcus is married to Theresa (Theresa Randle) and his daughter Megan (Bianca Bethune) had the baby. Hi son-in-law Reggie (Dennis McDonald) serves in the US Army. Reggie and Megan are not married yet.

Mike and Marcus had been partners for 25 years now. Desiring to spend more time with his family, the aging Marcus tells Mike he intends to retire, to Mike's chagrin. During a party celebrating Marcus' grandson, Marcus challenges Mike to a footrace. The bet being if Marcus wins they both retire, but if Mike wins they continue till the very end. Predictably Mike runs ahead of Marcus, but Mike is shot by Armando and left in a coma for months. Chastised by Isabel for targeting Mike first, Armando continues to assassinate other targets on his list during Mike's convalescence. The targets include the forensics expert, the prosecutor, and the judge who were all involved in his father's case.

AMMO had analyzed the bullets that hit Mike and found that they were custom rounds. But AMMO was not able to make any more progress on the case. Meanwhile Isabel finds out that Mike is still alive and asks Armando not to kill him till Mike has suffered as they have for all these years. In response Armando uploads a video shot by him using a helmet mounted camera, of him shooting Mike in the drive by shooting. The video goes viral and Mike realizes that the shooter is baiting and taunting him.

Following Mike's recovery, he is determined to seek revenge and unsuccessfully attempts to recruit the now-retired Marcus, causing a fall out between them. Mike violently obtains the identity of arms dealer Booker Grassie (Rory Markham) from an informant.

Realizing that Mike will not heed orders to stay away from the investigation, Captain Howard (Joe Pantoliano) reluctantly allows him to work with the tech-driven team in charge, the Advanced Miami Metro Operations (AMMO), led by Mike's ex-girlfriend Lieutenant Rita Secada (Paola Nunez). The AMMO is a small team trained in new tactics and investigative methods.

While the team spies on Grassie at an arms deal, Mike determines that the buyers intend to kill Grassie and intervenes, but fails to save him. Later, Marcus is called by Carver Remy (Ivo Nandi), an old informant who believes the assassin is after him. Marcus contacts Mike and the pair travel to Carver, but are too late to save him. Armando escapes after a fistfight with Mike.

Captain Howard later reveals his intentions to retire as well, offering advice to Mike that he needs to find a path forward in life. He is abruptly assassinated by Armando moments later. The Captain's death pulls Marcus out of retirement, but he intends to work as a team with AMMO. They track down Grassie's accountant, who leads them to Lorenzo "Zway-Lo" Rodriguez (Nicky Jam). They infiltrate Zway-Lo's birthday party leading to a destructive car chase. Armando arrives in a helicopter to rescue Zway-Lo but kills him when he blocks Armando's ability to shoot the pursuing Mike. As he lines up a shot, Armando tells Mike "Hasta El Fuego". Gunfire from Marcus creates cover for Mike, who falls into the river below.

AMMO is shuttered because of the failed operation. In private, Mike reveals to Marcus that Armando may be his son. He explains that, twenty-four years ago, before partnering with Marcus, Mike worked undercover in the Aretas cartel where he met Isabel. They fell in love and intended to run away together, using "Hasta El Fuego" as a made-up secret catchphrase. Mike ultimately remained loyal to the police, realizing how dangerous Isabel would become. Despite Mike's opposition, Marcus and AMMO join him in Mexico City to confront her.

At the Hildago Palace, Mike meets Isabel and scolds her for concealing the truth from him. A shootout quickly ensues between AMMO and Isabel's men. Marcus shoots the pilot of Isabel's support helicopter, causing it to crash into the central lobby and starting a fire. Marcus confronts Isabel, while Mike explains the truth to Armando. Armando begins beating on Mike, but he refuses to retaliate. Demanding the truth, Isabel confirms to Armando that Mike is his father. Isabel inadvertently shoots Armando in the chest while aiming for Mike. Enraged, she attempts to finish Mike, but Rita intervenes and shoots Isabel, sending her falling into the flames below.

Sometime later, Rita has been promoted to police Captain, while Mike and Marcus are placed in charge of AMMO. Mike visits a remorseful Armando in prison, offering him a chance to earn some redemption. Armando accepts.