Joe Pistone is an FBI agent working under the alias Donnie Brasco. He tries to gain the trust of one of the members of the gang - Benjamin "Lefty" Ruggiero. "Lefty" for the past 30 years remains as an ordinary "soldier", which is very hurt his pride. The piston with the "Lefty" quickly find a common language and become friends. Ruggiero even vouched for Donnie in front of his men and helped him to enter into a criminal clan. Soon Pistone surprisingly begins to realize that he no longer plays in Donnie Brasco, and really starting to get to them. New life gives him almost unlimited freedom, but to return as he still has the opportunity. Just need to betray the one who became a true friend.