Two convicts and small time crooks (Amitabh and Dharmendra) are picked by Thakur (Sanjeev Kumar), a former police officer, to seek vengeance on the dangerous bandit Gabbar Singh (Amjad Khan) because he killed all of Thakur's family (except a daughter-in-law) and maimed Thakur for life.This was a result of an earlier incident in which Thakur -- acting as a police officer -- had captured Gabbar and helped in his conviction in the court. Gabbar managed to escape and wreaked havoc in Thakur's life. Now Thakur seeks the help of these two crooks to get Gabbar. The ensuing action makes for one of the most exciting Indian movies made to date.