Sydney (Amy Adams) and Irving (Christian Bale) meet at a party and con people into giving $5,000 in exchange for a $50,000 payout that never comes. They are trapped by FBI agent Richie DiMaso (Bradley Cooper) who agrees to waive all charges against Sydney and Irving if they help him entrap four other con artists. Their plan is to coerce these men into deals by flaunting a multimillionaire sheik in front of them but one of Irving’s friends suggests they convince the sheik to invest in Atlantic City with New Jersey mayor Carmine Polito.
Irving befriends Carmine (Jeremy Renner), who really has the town’s best interest at heart, but does some unscrupulous deals to save money, including involvement with a mob boss named Victor Tellegio (Robert De Niro).
Afraid for their life, Irving and Sydney arrange a scheme where their friend poses as Victor Tellegio’s attorney and provides evidence that convinces the FBI to wire two million dollars into an account (to prove Tellegio accepted a bribe). But it turns out the account belongs to Sydney and Irving, who use the money as leverage to demand immunity and a reduced sentence for Carmine.
Throughout the film, there are love triangles between Sydney, Irving, and Richie, as well as Sydney, Irving, and his wife, Rosalyn (Jennifer Lawrence). Rosalyn falls in love with a member of the mob, leaving Sydney and Irving free to be together; Richie is left alone and a laughing stock at the FBI.