The film starts with Sanjay Dutt as a budding young actor, being directed by dad Sunil Dutt in his debut film, Rocky. It is evident quite early on that his father’s principles and image are too much for Sanjay to handle. Before one knows it, Sanjay falls into bad company and starts taking drugs. His friend and drug supplier is Zubin Mistry, also known as God (Jim Sarbh). The innocent stray incidents of doing drugs soon turn into an addiction which threatens Sanjay’s very life. The story also shows how Sanjay Dutt finds solace in substance abuse even while his mother, Nargis Dutt (Manisha Koirala), is battling with cancer at home, then in the hospital in the USA, and then again at home in India. It is during his US visit for his mother’s hospitalisation that Sanjay meets Kamlesh who would go on to become a very close friend and a confidant. Kamlesh flies from the US even when Sanjay needs him after his girlfriend, Ruby’s (Sonam Kapoor), father finalizes her marriage with an NRI boy.
Things come to such a stage that after his mom’s demise and his break-up with Ruby, Sanjay has to be put in rehabilitation in the USA. A reformed Sanjay returns with his dad from the USA. The bond between Sanjay and his friend, Kamlesh, grows very strong – so strong that Kamlesh is by Sanjay’s side whenever he needs him. Sunil Dutt has also seen a true family friend in Kamlesh and is very fond of him.
In 1993, after Sanjay has become a very popular and successful Bollywood star, he is arrested for possession of an AK-56 rifle without a license. The media brands him a terrorist because the gun episode happens soon after the serial bomb blasts in Bombay in 1993. Sanjay Dutt is jailed. His father and family are devastated but stand behind Sanjay. Despite Sunil Dutt’s connections, nobody is willing to help because the draconian TADA has been slapped on Sanjay. Kamlesh is like a true pillar of strength in these trying times.
One day, Sanjay gets bail. But there comes a time when even Kamlesh severes all ties with Sanjay Dutt after it is reported by the media that a truck with RDX had been found parked in Sanjay Dutt’s compound. Kamlesh, who is in Sanjay’s home in India at that time, leaves for the USA, telling Sanjay that the friendship would have to end here. The Dutt family goes through hell as the legal battle goes on for years. Sunil Dutt passes away. Just a day before he breathes his last, Sanjay had prepared a speech which he was supposed to make on a public platform, in praise of his father. In that speech, he was to convey his true love for his father with whom his relations had been strained for obvious reasons. But Fate had so intervened that the contents of the speech were never conveyed to Sunil Dutt.
Years later, the final decision in Sanjay Dutt’s gun possession case is pronounced by the Supreme Court. Although he is held guilty under the Arms Act for illegal possession of a gun, he is acquitted under the TADA. He is given a five-year jail term. Before going to jail, he contacts celebrated author Winnie Diaz (Anushka Sharma) to write his side of the story to tell the world that he isn’t a terrorist. At first reluctant, Winnie agrees to pen his biography but mid-way, decides against it. Her dilemma increases when she meets Sanjay Dutt’s estranged friend, Kamlesh, in the USA. Finally, Maanayata Dutt (Dia Mirza) gives Winnie a recording of Sanjay Dutt’s radio show which he hosts in jail.