NOTE: This spoiler was submitted by Jeremy

The film starts with Detectives Mike Lowery (Will Smith) and Marcus Burnett (Martin Lawrence) speeding through the streets of Miami with other cops following them. They arrive at a hospital and run inside as they head to the room where Marcus’s daughter Megan (Bianca Bethune) has given birth to a baby boy. His wife Theresa (Therese Randle) and Megan’s fiance Reggie (Dennis Greene) are there as well, informing Marcus that the boy is named after him. He proudly holds his grandson.

In a Mexican prison, inmate Isabel Aretas (Kate Del Castillo) is muttering an incantation that draws a guard’s attention. Isabel grabs a knife off the guard and stabs her, with the other inmates jumping in and stabbing her to death. Other guards take Isabel outside, only for her son Armando (Jacob Scipio) to help her kill off all the other guards. He frees her, and they return to their home to plot revenge on behalf of her late husband Benito, with Mike being their intended final target.

Armando goes to the docks to pull out a crate filled with money with intent to work with other gangsters, but these gangsters try to screw him over and take the majority shares of the money. With their guns drawn on Armando, he retaliates by stabbing everyone rapidly. He then orders the remaining men to step up if they wish to work loyally under his family. A crook named Lorenzo Rodriguez, AKA Zway-Lo (Nicky Jam), joins him.

Mike and Marcus’s fellow officers, including Captain Howard (Joe Pantoliano), gather at a bar to celebrate Marcus becoming a grandfather. They encounter a woman named Rita (Paola Nunez), who has just been promoted to lieutenant and is also Mike’s ex. She informs them that she is also now heading AMMO (Advanced Miami Metro Operations), which employs a younger team of officers. Marcus knows they are getting too old for all the crazy things they used to get into, and he urges Mike to settle down, though he disagrees. The two go outside to have a foot race, and as Mike takes the lead, Armando rides up on a motorcycle and shoots Mike down. He gets away as the officers rush to help Mike.

Mike is in critical condition. Marcus prays to God that Mike be saved, with the promise that Marcus will never bring anymore violence into the world. Rita and Howard then order AMMO – Kelly (Vanessa Hudgens), Dorn (Alexander Ludwig), and Rafe (Charles Melton) – to do what they can do investigate Mike’s shooter. Meanwhile, Isabel chastises Armando for going after Mike so soon, as she deliberately wants him to die last so that he suffers watching others die. They proceed to go after a judge, a forensics analyst, and a prosecutor, killing them all in broad daylight.

Six months later, Megan and Reggie get married, and Mike has recovered from his injuries. He delivers a speech at the wedding before later asking Marcus to help him catch the shooter, but Marcus refuses, fearing someone else will get hurt, and he insists that he is retired. After learning Mike is awake, Armando uploads his bodycam footage of him shooting Mike. He goes to Rita for help but is also met with the same refusal.

Mike takes it upon himself to find his shooter. He visits a retired criminal named Manny The Butcher (DJ Khaled) and beats his hand with a hammer until he gives up the name of a guy named Booker Grassie (Rory Markham), who would have info on the owner of the motorcycle, and therefore the shooter. Mike goes to Captain Howard, who begrudgingly has him go along with AMMO to find Grassie. Mike quickly butts heads with Rafe since he’s a smartass, but Kelly and Dorn respect Mike’s status as a detective.

Mike and the team go to a warehouse where Grassie is going to make a drop. Mike quickly catches that Grassie is trying to rip the guys off and will get himself killed. A shootout begins, and Mike tries to get Grassie out of there, but after fighting off the other thugs, Grassie is blown back by an explosion and is impaled by a forklift. He dies before Mike can get any info out of him.

Marcus gets a call from a snitch named Carver Remy (Ivo Nandi), who claims that Armando is following him and trying to kill him. He asks Marcus for help, who then tries to contact Mike, but he ignores Marcus since he sees him as a quitter. Eventually, Mike picks up and joins Marcus in going to find Remy, but once they get to his hotel, Remy’s body hits Marcus’s (actually Theresa’s) car. Mike runs into the hotel and fights Armando, managing to pull his mask off but finding himself stunned when he sees Armando’s face. He manages to get away.

Mike later joins Howard at a game, where the two bond as Howard expresses his genuine concern and care for Mike. As they are leaving, a bullet strikes Howard in the throat. Armando and Zway-Lo are behind it, but since Mike knows he is in plain sight, he pulls Howard away and stays behind a car, giving Armando no clear shot. Mike tries to revive Howard, but he dies. After his funeral, Marcus officially decides to join Mike in catching the shooter.

Mike and Marcus go off to find a shady broker named Picante Jenkins (Happy Anderson) for a lead on their shooter. They enter Jenkins’ motel room where he is coked out of his mind. Marcus tries to appeal to him on a personal level, but it only gets him punched hard. AMMO soon comes in, with Marcus having called them, and they tase Jenkins to the ground. After getting Jenkins’ files, they recognize Zway-Lo and plan to track him next.

The team goes to a club where they find Zway-Lo. After attempting to arrest him, he runs for it, and the team must fight his goons. Mike and Marcus hop on a motorcycle and sidecar, with Marcus having to break his promise to God and use a machine gun to fight off the incoming thugs. They ride into the streets to pursue Zway-Lo, who then attempts to board a chopper ladder. Mike runs off and latches onto the ladder as well. Armando shoots Zway-Lo off to get a better shot at Mike. He tells him “Hasta el fuego” before Mike lets go and falls into the water.

Back at headquarters, Mike has Dorn look up files based on the phrase Armando said. Mike realizes Isabel is behind all of this. He explains to Marcus that before they teamed up, he was deep undercover in the Aretas cartel and he had a relationship with Isabel before he had to throw her in jail and get her husband killed. “Hasta el fuego” was a phrase they came up with that was nonsensical but was supposed to mean “Together until the flame burnsout.” She was also heavily into witchery, which gave her the nickname “La Bruja”. Mike concludes that Armando is his son and that she has been grooming him for revenge, since all the victims were on the same case against the Aretas family. After realizing he knows the truth, Isabel contacts Mike and arranges for him to meet her in Mexico City to end things.

The team heads to Mexico for the showdown, with Isabel ordering Mike to meet them in an old palace. They engage in a firefight against Isabel’s mercenaries, with the AMMO officers proving their skills with guns, as well as physically in Dorn’s case. Marcus then shoots down a sniper chopper, causing it to come crashing down to the building and starting a fire. Armando goes to fight Mike, but he decides to confront him as a person and reveal his parentage to Armando. He asks Isabel if it’s true, and she admits that it is. She tries to shoot Mike, but Armando steps in the way and takes the bullet in the shoulder. Rita then shoots Isabel off the ledge, sending her plummeting into the flaming wreckage. Marcus almost falls over too, but Armando helps Mike pull him up and get them out of there.

Later on, the team is getting along better and they celebrate as Rita has been promoted to become the new captain. Mike and Marcus then bond with Baby Marcus, singing the “Bad Boys” song to him.

Before the credits roll, Mike visits Armando in prison, offering him a chance to make up for his crimes. Armando appears to be interested.

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Detectives Mike Lowery and Marcus Burnett are still great friends and partners, but after Marcus becomes a grandfather, he realizes they are too old for all the trouble they have gotten into, while Mike is still enjoying the action. A shooter on a motorcycle then makes an attempt on Mike's life, putting him in critical condition. Marcus officially chooses to retire after praying for Mike's recovery.

The perpetrator is Armando Aretas, son of Isabel, a former cartel leader out for revenge against Mike. They kill other men involved in the case against her family, including Captain Howard. This is what pushes Marcus to join Mike in taking the villains down. They must team up with AMMO, a younger team of officers, to catch them.

Mike then learns that he is Armando's father, as he was in a relationship with Isabel before she was thrown in jail since he was undercover investigating their cartel. Isabel has the team face her in Mexico. The team kills her goons before Mike tells Armando he is his son. After Isabel confirms this, she tries to kill Mike, but Armando takes the bullet (non-fatally). AMMO leader Rita shoots Isabel, who falls off a ledge into a flaming wreckage.

Armando is arrested, but Mike offers him a chance at redemption. Mike and Marcus also remain good friends and partners.