In a locomotive, Thakur Baldev Singh, a police inspector, is pursuing the two thugs Veeru (Dharmendra) and Jai (Amitabh Bachchan) when he stumbles between two cars and is on the verge of a fatal fall. However the two bandits sympathize and manage to draw it from this posture.
Law requires, Veeru and Jai are sent to prison, but Detective Inspector Singh acknowledges promises to do his utmost to shorten their sentence.
Later, Detective Thakur Baldev Singh manages to capture Gabbar Singh (Amjad Khan), a tyrannical leader who ruthlessly terrorizes the region. Gabbar Singh, terribly furious at being caught, manages to escape and prepares retaliation against the inspector.
The years have passed, Thakur Baldev Singh is now retired. He returns to settle in his village and discovers a frightful spectacle: his family murdered by the men of Gabbar Singh. Enraged by a burning desire for revenge, the ex-inspector brings Veeru and Jai out of jail, who once saved his life. They are immediately engaged as bounty hunters, and must bring Gabbar Singh alive to Thakur Baldev Singh.