미국으로 이민온 아일랜드인 Jessie인 할아버지와 고기도매상인 아들 Vito 그리고 명석한 장학생인데 휴학중인 손자 Adam 이 함께 연구자료를 빼내는 story.
Jessie McMullen (Sean Connery) is a Scotch-Irish American widower who emigrated with his Sicilian wife to New York in September 1946. A lovable rogue, incorrigible womaniser and tough guy, Jessie is proud of his criminal past and lifestyle. He raised son Vito (Dustin Hoffman) to follow in his footsteps, but Vito went straight at 21 when his son Adam was born. Vito now runs a thriving wholesale Twelfth Avenue meat-packing warehouse and has left his criminal life behind.
Ashamed of his family's past, Vito married his middle-class Jewish sweetheart and has tried set a good example for their son, which in his mind means keeping Adam (Matthew Broderick) away from his criminally minded yet charming grandfather. Little does Vito know that this strategy has backfired, the mystery surrounding Jessie, coupled with his strict educational upbringing, causing Adam to idolize his grandfather. Adam even puts up bail, borrowing it from Vito, one night after Jessie is charged with assault from a bar fight.
Adam is in college with a scientific scholarship and has a bright future. However, six months before graduating, he drops out, complaining to Jessie that he was already "being put on a pension plan and they had my whole future mapped out." So when he unveils a scheme for a burglary, it impresses his grandfather, but Vito is shocked and bitterly disappointed. He warns his son not to pursue this and even slaps his face in a bar to drive home the point. This pushes Adam even closer to his grandfather, who can't wait to take a shot at a million-dollar payday.
Jessie is eager to re-enlist his reformed son Vito, calling the scheme "the sweetest deal of my life." The more he hears, the more tempted Vito is to give up the safe but dull life he has carved out for himself and return to the wild days of his youth. So the three generations of McMullens embark on one great criminal adventure, Vito begrudgingly saying yes on the premise that he is there to watch out for Adam along the way.
The plan is to steal valuable scientific research from a lab. It backfires horribly when, having seemingly pulled off the heist successfully, Adam forgets to take a logbook that is a vital prerequisite to being paid the million dollars. Adam dashes back into the building to retrieve it, but in his haste he sets off an alarm on his way out. Vito and Jessie can only watch helplessly from afar as Adam is captured by the police. At the last minute, Adam manages to throw the logbook over a fence.
Vito is heartbroken and dreads his wife Elaine finding out what has happened. He and Jessie hire an expensive shyster lawyer for Adam's defense, but are told the only way for Adam to avoid a 15-year sentence is to give up his two mystery accomplices and "the goods" taken in the heist. Vito's wife angrily instructs him to give himself up along with Jessie, whatever it takes to get Adam a reduced sentence. Vito locates the vials stolen from the lab that Jessie's girlfriend Margie has been safekeeping, Margie instructing him to "get that kid out of jail."
Discovering that the scientific research they stole had been faked, Jessie tracks down Adam's former professor Jimmy Chui (who had double-crossed Adam by selling him on the robbery idea) and makes him pay. A crestfallen Vito, meanwhile, gives in to his wife's suggestion that he give himself and his father up. He turns over the stolen goods, whereupon Jessie is placed under arrest.
A judge finds all three McMullens to be at fault, but after generously placing both Vito and his son on probation, he throws the book at Jessie, giving him a 15-year sentence, tantamount at his age to a life behind bars.
Adam visits his grandfather devotedly in jail while banning Vito from his life. Vito's explanations that he did what he did for Adam's own good fall on deaf ears. Adam calls him a "piece of garbage" and lambasts him for having "ratted out your own father."
Jessie's health takes a turn for the worse. He dies in prison, as Vito arrives minutes too late to say a last goodbye. As the body is being carted away, he breaks down in tears.
Vito and Adam eventually make their peace months later. Vito agrees with Adam that the most fun they have had as a family was the caper. Together, they give Jessie a grand sendoff, scattering his ashes from the roof of Vito's childhood home.
