Jai (Amitabh Bachchan) is an expert gambler, has been for as long as he can remember, and has never lost a game. These skills bring him to the attention of the underworld don Ratan Das (Madan Puri), who is interested in hiring him to win large amounts of money from rich people and then influencing them into doing whatever he wants. Jai agrees to do so, and plays successfully, though unknowingly to entrap Nath (Jagdish Raj), who works for the government. After losing large amounts of money, he is blackmailed into revealing the blueprints of a top-secret military laser weapon that can hit any target within 50 miles and is wanted by another underworld don named Saxena (Utpal Dutt). When the Indian police come to know of this, they assign the case to Inspector Vijay (also Amitabh Bachchan), who is a lookalike of Jai.