First-time crook Sonny Wortzik (Al Pacino), his friend Salvatore "Sal" Naturale (John Cazale), and Stevie (Gary Springer) attempt to rob the First Brooklyn Savings Bank. The plan immediately goes awry when Stevie loses his nerve shortly after Sal pulls out his gun, and Sonny is forced to let him flee the scene. In the vault, Sonny discovers that he and Sal have arrived after the daily cash pickup, and only $1,100 in cash remains in the bank.
To compensate, Sonny takes a number of traveler's cheques, but his attempt to prevent the cheques from being traced by burning the bank's register in a trash can causes smoke to billow out the side of the building, alerting the business across the street to suspicious activities. Within minutes, the building is surrounded by the police. Unsure of what to do, the two robbers camp out in the bank, holding all the workers hostage.