D. N. Tripathi, a lyricist portrayed by Piyush Mishra, embarks on the ambitious task of writing a biography about Sanjay "Sanju" Dutt, played by Ranbir Kapoor, drawing parallels between Sanju's life and that of Mahatma Gandhi. However, a surprised Sanju quickly dismisses him from the premises. Following the verdict delivered by the Bombay High Court regarding the 1993 Bombay bombings, Sanju finds himself sentenced to five years in prison under the Arms Act. In a twist of fate, Manyata Dutt (played by Dia Mirza) reaches out to Winnie Diaz (portrayed by Anushka Sharma), a writer based in London, urging her to pen Sanju's biography to provide his perspective to the world. Initially hesitant, Winnie becomes intrigued when Zubin Mistry (depicted by Jim Sarbh) advises her against the project.
Winnie meets Sanju for the first time, and this leads to a revealing flashback of his tumultuous life. As a young man, Sanju's father, Sunil Dutt (played by Paresh Rawal), embarks on a quest to establish Sanju's acting career with the film "Rocky" (1981), where he serves as the director. Bound by his father's strict rules, including a ban on smoking on set, Sanju is persuaded by his friend Zubin to experiment with drugs. Tragedy strikes when he discovers that his mother, Nargis (enacted by Manisha Koirala), is battling cancer and needs treatment in New York. This personal crisis leads Sanju down a dark path of alcoholism and drug dependency.
While in New York, Sanju befriends Kamlesh Kanhaiyalal Kapasi (portrayed by Vicky Kaushal), a devoted admirer of Nargis. Kamlesh instills hope, praying for Nargis's recovery, and works to help Sanju overcome his addiction. As Nargis regains her health and the family returns to Mumbai, Sanju learns that his girlfriend, Ruby (played by Sonam Kapoor), is being pushed into an arranged marriage due to his destructive habits. In a bid to salvage their relationship, Kamlesh persuades Ruby to marry Sanju at a registrar’s office. However, after witnessing his intoxicated state, Ruby walks away, leaving Sanju heartbroken. The death of Nargis, just before the release of "Rocky," devastates him emotionally.
In a dire attempt to reclaim his life, Sanju agrees to check into a rehabilitation center in the United States, where he ultimately finds redemption with the support of his father and Kamlesh. Upon returning to India, he confronts Zubin, who had exploited Sanju’s vulnerabilities by selling him drugs disguised as expensive substances.
Kamlesh, now distanced from Sanju, shares the later chapters of Sanju's life with Winnie. By the late 1990s, as Sanju channels his energy into bodybuilding, his acting career sees a resurgence. Amid political turbulence following the 1992 Babri Masjid demolition, he acquires illegal weapons for his family's protection, landing him in trouble as he is arrested in 1993 for possession of firearms allegedly supplied by the D-Company.
Sunil Dutt valiantly fights for his son, ultimately securing bail after 452 days. Despite efforts to clear his name, media allegations tarnish Sanju’s reputation, leading even Kamlesh to sever ties, convinced of his guilt. After his release in 1997, Sanju faces a string of unsuccessful films until landing a role in "Munna Bhai M.B.B.S." (2003), which revitalizes his image and brings pride to his father. Tragically, Sunil passes away shortly after, leaving Sanju to contend with the fallout of his past.
The Bombay High Court later finds Sanju guilty under the Possession of Arms Act, leading to another arrest in 2013, with an upheld conviction by the Supreme Court. Insistent on his innocence, Sanju discusses the tainted media narrative with Winnie and Kamlesh, eventually released in 2016. Upon his release, he learns of Winnie’s completed biography titled "Kuch Toh Log Kahenge," named after one of his father's cherished songs. As his family reconciles with Kamlesh, Sanju reflects on his tumultuous journey, his past mistakes, and newfound hope for the future.
