Set in Los Angeles, California, the film opens with an armored truck making a stop at a coffee shop. Within moments, a team of robbers led by Ray Merrimen (Pablo Schreiber) attacks and tries to break into the truck. The guards attempt to defend themselves and stand their ground, leading to the robbers to kill them. Police officers arrive on the scene and engage in a shootout with the robbers. Eventually, Merrimen and his crew make off with the truck, but he reprimands Donnie (O'Shea Jackson, Jr.) for killing the first guard.
In the morning, Detective Nick "Big Nick" O'Brien (Gerard Butler) goes to investigate the crime scene. He has been investigating Merrimen and his crew for a while, whereas Merrimen holds a grudge with Nick for killing one of his guys.
Nick finds Donnie at the bar he works at and makes friendly chat before later cornering Donnie in his car and knocking him out. Nick brings Donnie to a house where his gang of officers interrogate Donnie over Merrimen and his plans. Donnie explains that he only got in with Merrimen and his crew because he's a great getaway driver and Merrimen was impressed with his skills. Through a flashback, we learn that Merrimen is planning to rob the Federal Reserve on Friday of that week, with the intention of taking roughly $30 million in unmarked bills that would otherwise get shredded.
Nick has Donnie sneak into the Federal Reserve by having him get hired as a Chinese food delivery guy and having him go through the vents to scope that place out.
At home, Nick's wife Debbie (Dawn Olivieri) discovers that Nick has been going behind her back seeing other women, particularly strippers. She angrily packs up her things and takes their daughters with her. Despite Nick's pleas to hear him out, Debbie hurls obscenities at Nick and hits him. She later has a lawyer go to his job and serve him divorce papers.
Nick spots Donnie at a restaurant with Merrimen and his crew, which makes them suspicious when Nick calls Donnie out. At their hideout, Merrimen has his right-hand man Levi (Curtis "50 Cent" Jackson) hit Donnie and interrogate him to make sure he hasn't been talking to Nick about their plans. Donnie assures him that he hasn't told him anything about the robbery.
Nick goes to a strip club and goes home with a stripper. In the morning, Merrimen finds him but does nothing, having found him because he set the stripper on Nick to get info on him.
Later on, Levi's daughter has a date come over to pick her up for a school dance. Levi pulls the guy aside to introduce him to Merrimen and the rest of their crew to intimidate him and make sure he does nothing to hurt Levi's daughter, or else the boy will utterly regret it. When he leaves, Merrimen and the guys have a laugh.
Meanwhile, Nick drunkenly crashes a small get-together between Debbie and some of her friends. He gets aggressive with one of the men before he is told to leave. Outside of work, however, Nick makes an effort to see his daughter.
The day of the heist comes. Merrimen and his crew invade the bank and take hostages. Nick and his guys are outside as the chaos unfolds. The Chief of Police calls and speaks to the bank's branch manager on behalf of Merrimen. To prove they are serious, Merrimen has one of his guys take a hostage to a back room and shoot her. Merrimen tells the manager to tell the chief that they want their large sum of money and a chopper. The thieves then blow the vault open and escape through a hole in the floor before Nick and his guys come in. They also find that the hostage they supposedly shot is still alive, but terrified.
Donnie is at the main building to ensure the gang is getting their money. He finds the cash and stashes it in bags. He once again acts as a delivery boy, but he gives the customer a bag of food he left in the vent days earlier. The customer tries to get security to stop him, but Donnie is gone. Nick and his guys catch up to him and capture him, beating him until he tells them where Merrimen is going.
Merrimen has cut Donnie and another guy off the team. As they try to make their escape, they hit a traffic jam and are blocked. Nick and his guys spot them and get out of their cars with guns as Merrimen and his guys try to escape. After warning other drivers, the police start to shoot at Merrimen and his gang. Levi and the other men are shot dead, but Merrimen keeps running. Nick chases after him and shoots him through a fence, wounding Merrimen. Nick hops the fence to catch him, but Merrimen refuses to go out quietly. Although he tries to fight back, Nick shoots Merrimen dead.
When Nick goes to inspect Merrimen's van, he finds bags with shredded money. He also finds that Donnie has escaped custody.
Nick later goes to Donnie's bar and sees pictures of him with some of the crew members from the heist. Through flashbacks, we see that Donnie had always planned for everything to go his way, including teaming up with Merrimen, switching out the cash bags with the shredded bills, and then escaping and getting away with the real money for himself. The realization hits Nick at how he was so easily fooled by Donnie.
In the final scene, Donnie is now in London, England working at another bar. His crew is nearby having drinks and enjoying the spoils of their victory. A man from a shop across the street comes in. Donnie serves him and asks if he works at the diamond shop. The man says yes, and Donnie gives the man a beer on the house.