Zanjeer (1973)

This fiery action oriented thriller opens on Diwali with the death of young Vijay Khanna's parents, and the only clue to the identity of the assailant is that he wore a charm bracelet with a white horse on it.

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), 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.
Various dealings of the underworld continue unabated throughout the town, all tracing back to gang leader Teja (Ajit Khan).

A mysterious caller continually phones Inspector Khanna to inform him exactly when a crime is about to take place, but hangs up before Khanna can extract any more information out of him. When a traffic accident perpetrated by gang members leaves several children dead, a witness, a street performer named Mala (Jaya Bhaduri), is bribed by Teja's men to keep quiet.

When she is questioned by Vijay, he becomes enraged at her denying she knows anything, and, to sway her differently, takes her into the morgue to view the mangled bodies of the children. She has a change of heart, and comes clean, asking that the bribe be donated to an orphanage. She identifies the man behind the traffic accident.

Once it is known that Mala has broken her word, Teja's men come after her. She is chased through the night, narrowly escaping across the train tracks, and coming to Inspector Khanna's house, desperate for shelter. He lets her in, allows her to stay, and the two discover that they are both orphans, and discuss the fears associated with living alone. Khanna kindly takes her to his brother and sister-in-law, and, under the sister-in-law's tutelage, Mala begins to learn how to keep house, as well as English, and other refinements.

Eventually, Vijay is framed for bribery, stripped of his title and position as inspector, and jailed for 6 months on false charges, trapped by Teja. When he is released from jail, he plans to take revenge. Mala, by this time, has developed from a frightened stranger seeking his help to a romantic interest for him. She begs him to seal their relationship, that he must stop being so vengeful.

He agrees, but soon must come to terms with such a promise when he meets, in a Christian cemetery, the informant who had called him in the past when he was an inspector. The man, De Silva (Om Prakash), appears half-insane, holding onto an empty bottle. He says that on Christmas several years before, his three sons drank poisoned moonshine, and died from it. Until the killer is found, he will continue to wander with the bottle.

When local criminals mocked him and called him crazy, he vowed to get back at them as he could: by phoning the inspector when a crime was about to happen.
After hearing this news, Vijay becomes depressed, torn between his desire to help the grieving De Silva, and his need to keep his promise to Mala that he would not take any more revenge on the lowlifes of the town.

Eventually, along with a concerted effort by Sher Khan to cheer up Vijay, Mala relents, vowing she will not try to control him, and says he must do what is right.
The trail of tainted moonshine leads back to Teja and his men. Upon finally cornering the crook on Diwali, fireworks bursting overhead, Vijay also finds out that the person who murdered his parents, 20 years ago, on the same night, is Teja, recognisable by the zanjeer on his wrist.

Sher Khan helps him to fight Teja and his men, and take justice into their own hands, until the police arrive. When the hapless police inspector is held at gunpoint by Teja, Vijay manages to drop to retrieve a pistol from the ground, and shoots him dead, his body falling into the swimming pool.