Sonny (Curtis "50 Cent" Jackson), Vince (Ryan Phillippe) and Dave are childhood friends and low-level crooks who decide to pull off a heist in broad daylight, stealing valuable diamonds from a merchant in a limo. After the robbery, Vince double-crosses the other two, shooting them and taking the diamonds. Dave is killed, but Sonny survives and swears revenge.
The limo driver is actually Vince's sister, who is also in on his plan. Vince actually needs the money for his father William (James Remar), who's in jail and has been targeted by the other inmates. Vince wants to pay off the prison officials to grant his father protection away from the prison's general population.
Meanwhile, a recovered Sonny goes around the city, stealing from bookies while searching out Vince. This brings him to the attention of no-nonsense crime boss Mr. Biggs (Bruce Willis), who forces Sonny into his employ in exchange for help. He is sent out along with Biggs' muscle, Petey (Randy Couture) to steal some money from some Russian thugs. After the robbery, they make a stop at a dealer friend of Sonny's to buy some pot, where Petey accidentally shoots himself in the head while playing with some guns. Sonny disposes of the body, but keeps the money for himself. Biggs begins to violently interrogate the Russian hoods.
Meanwhile, the Iranian cartel which owns the diamonds sends out a hitman to retrieve them. He gives Sonny a week to return the goods, and pays a visit to Vince's sister, whom he beats to death.
Sonny lies to Biggs, telling him that it is actually Vince who has his money. They set up a meeting which turns into a shoot-out, where Biggs and his men are all killed. Vince escapes and makes it back to his apartment, where he is visited by the Iranian hitman, whom he kills after discovering it was him who killed his sister.
Vince flees with the money from the diamond heist, but is quickly found and subdued by Sonny, who takes him to a quarry and forces him to dig his own grave at gunpoint. A desperate Vince reveals the real reason he betrayed his friends and regrets what he did. Realizing that it's not worth it to kill him, Sonny shoots him in the leg and leaves him alone with his guilt.
Since Vince doesn't deliver the money to the prison officials, the unprotected William is murdered by the other inmates. Sonny sends the money to Dave's widow and leaves town.