Joey and Monica are arrested by Det. Laurenzi while attempting to flee the country. Joey is later acquitted of taking the money due to temporary insanity.
Based on a true story and set in 1981, Joey Coyle (John Cusack) is an unemployed dockworker from South Philadelphia who lives with his mother, brother Billy (James Gandolfini), and Billy's family. One day, Joey finds $1.2 million on the street that fell out of the back of an armored truck heading for Atlantic City. Joey immediately decides to keep it and begin to live the life he feels he deserves. Meanwhile, Detective Laurenzi (Michael Madsen) of the Philadelphia PD is assigned to the case of the missing money.
That night, Joey begins spending the money, and since the entire $1.2 million was in $100 bills, the sight of an unemployed dockworker suddenly spending $100 bills gets everyone's attention. He tells various stories as to how he suddenly got rich, such as hitting on a longshot at the racetrack. Joey then goes to childhood friend Dino (Benicio Del Toro), who works for a low-level gangster, to get the money laundered. They agree to launder half the money now and the other half later. Joey also meets his ex-girlfriend Monica (Debi Mazar), who is now an investment banker, for advice to what to do with the money. They soon get back together and she begins helping Joey deal with the money.
Throughout the movie, Laurenzi's investigation leads him closer to Joey, while everyone else is figuring out that Joey's stories of how he suddenly got rich isn't adding up. Also throughout the movie, we hear several conversations from the city's residents about the money, and many of them see the man who took the money as a hero, not a criminal, and would have done the same thing he did. One night, while trying to hide the money in the attic, Joey falls through the ceiling, revealing the money to everyone in the house. An enraged Billy tells Joey he has one day to either return the money or get out of his house forever. Soon, the entire neighborhood learns that Joey has the money. But instead of turning him in to the police for the reward, they promise to protect him. They also see Joey as a hero instead of a criminal.
Later, Joey and the mob have a disagreement over how they are laundering the money. Joey wanted the laundered half of his money before he turned over the second half, but the mob now wants all of the money upfront. After Joey threatens the gangsters, Dino is ordered to kill Joey and get the rest of the money. The regulars at the neighborhood bar, headed by Billy, protect Joey from Dino, but then tell him that he has to leave town. Joey and Monica decide to flee the country with the remaining money.
Laurenzi's investigation finally points to Joey as the man who took the money, and his identity is revealed on the news. He also learns of Joey's plans to leave the country, and goes to the airport, where he arrests Joey and Monica just as they are about to board a flight to the Bahamas. As they are led away in handcuffs, the onlookers cheer Joey and treat him as a celebrity. Title cards at the end of the film say that Joey was acquitted of taking the money due to temporary insanity.