The film opens on Diwali with the murder of young Vijay Khanna's parents, committed by a man of unknown identity with a white horse on his charm bracelet, "zanjeer". Because of this traumatic event, Vijay has recurring nightmares of a white stallion. Even as a child Vijay stays socially awkward and stays away from the other kids, showing the audience that he believes himself to be alone. Fast forward 20 years, and Vijay (Amitabh Bachchan) is now an inspector, an honest police officer in a town where few are just. He receives complaints about a local man, Sher Khan (Pathan) (Pran (actor)), who is running gambling dens. When he calls Khan in for questioning, Khan's superiority complex chafes against Khanna's police authority, as he scolds the officer, telling him he only orders him around due to the uniform he wears. Vijay takes him up on his challenge, and meets him in street clothes to fight him. At fight's end, Sher Khan not only closes his gambling dens, but has gained respect for Vijay. He becomes an auto mechanic, and reforms his ways.