Miles Logan, played by Martin Lawrence, is a professional thief who steals a valuable diamond worth $20 million with his team. However, things go sour when one of his partners double-crosses him and tips off the police. Logan is forced to stash the diamond in an air vent before being caught and imprisoned for two years.
On his release, Logan returns to the construction site where he stashed the diamond to retrieve it. However, he discovers that the site is now occupied by a new police station. Logan decides to pose as a detective in order to gain access to the building and retrieve the diamond.
The plan seems to be working until he is assigned a rookie partner, played by Luke Wilson, who is eager to impress him and help solve a re-opened case. Logan must balance his need to find the diamond with his new duties as a cop, leading to many humorous situations as he tries to maintain his cover.
As Logan continues to search for the diamond, he starts to form relationships with his colleagues and even falls for a woman that he meets during his investigation. However, as the pressure mounts, he must race against time to recover the diamond before his cover is blown and he is caught by the police.
In the end, Logan gets the diamond but realizes that he has grown attached to his new life as a cop. He decides to return the diamond and turn himself in, leading to a final comedic twist in the movie.