Marcus Burnett (Martin Lawrence), the quite family man and Mike Lowrey (Will Smith), the reckless ladies man are Miami policemen who are assigned to recover a $100 million drug shipment before it gets distributed and they have only 72 hours to do it.
Mike and Marcus still work together as narcotics cops in Miami, but Mike is hiding the fact that he is dating Marcus's sister. Their boss, Captain Howard, gives them a new assignment regarding the flow of ecstasy pills into Miami.
Now a police inspector, Marcus Burnett teams up with Mike Lowery as they face off against a pair of drug lords, who are, in fact, a mother and a son, all while previous vendettas are chasing them.
After the events that took place in the third part, when a new threat appears in the city of Miami from some bad boys, the police must confront them forcefully and firmly while imposing control.