In order to crack down on the mafia forces, the FBI assigned agent Joe Pistone to infiltrate the mob undercover under the alias Donnie Brasco. Through a jewelry deal, Joe met the mob boss Benny Ruggiero and earned his favor. To gain Ruggiero's trust, Joe had to commit all sorts of crimes. However, as he spent more time with Ruggiero, Joe developed a friendship with him and his attitude towards people and things changed. Due to his over-involvement in work, he also neglected his family's feelings, causing a rift with his wife. During this period of hesitation, he failed to send intelligence to the FBI on time, while Ruggiero, unable to contain his ambition for power, plotted with Donnie to take out the boss. Unexpectedly, because the FBI lost contact with Joe for too long, they sent someone else to track and monitor, leading to the exposure of Ruggiero's plan. The situation took a sudden turn for the worse...