Omkara “Omi” Shukla, is the titular Omkara. He is the leader of a criminal gang working for a local politician, Tiwari Bhaisaab. Omi works closely with his two most trusted associates, Ishwar “Langda” Tyagi and Keshav “Kesu Firangi” Upadhyaya; the three form a triumvirate of the most feared bahubali or political enforcers in their region. The film opens with Langda Tyagi barging in on a baraat, a traditional Indian wedding procession. Here he challenges the groom, Rajju, taunting him to try and stop Omkara from kidnapping Dolly Mishra, the bride. Rajju does not succeed in preventing the abduction and as a result the wedding never happens.
The father of the kidnapped bride is an influential and highly respected lawyer, Raghunath Mishra; livid at such a brazen crime he meets up with Omi and threatens him at gunpoint to return his daughter. Tiwari Bhaisaab mediates between the two, pointing out how volatile the political landscape is at present and that a murder would only result in vendetta. Still grieved by the affront, Bhaisaab, resolves the situation by having Dolly tell her father that she eloped with Omi and was not taken against her will. She also confides that she had fallen in love with the Omkara, embarrassing her father greatly. He leaves the meeting feeling betrayed but before departing completely he warns Omi that if she was capable of deceiving her father, she may also in time deceive him.
Omi manages to successfully remove Bhaisaab’s political rivals through a combination of violence and blackmail. Bhaisaab, as a result, wins a seat in parliament and Omkara is moved up from bahubali to a candidate for the next state elections. Once Omi enters the political arena he appoints Kesu, bypassing Langda as his second in command. This decision angers Langda as he believes Kesu, a younger man, to be inferior to him. Badly embittered, Langda plots vengeance against his former commander. Knowing that Kesu cannot hold his drink, he initiates a drinking session that ends in a brutal confrontation between Kesu and Rajju. This scandal infuriates Omi who must now be more careful of whom he associates with because of his political career. Omi begins to question his decision of choosing Kesu.
Having discredited Kesu, Langda now moves the second phase of his plan into action. He then convinces Kesu to plead his case with Dolly, Omi’s new wife-to-be. Langda implicates that Kesu’s visits to Dolly are anything but innocent, hinting that an affair has sprung up between the two. Dolly carelessly drops a kamarbandh, an ornate waist belt worn by Indian women, which is in turn stolen by Langda’s wife, Indu. The stolen belt makes its way to Billo Chamanbahar as a token given by Kesu--eventually taken as hard evidence of Dolly’s perfidy.
The film reaches its tragic climax on Omkara’s wedding night. Consumed by a jealous rage, Omi strangles his new wife to death and orders Langda to shoot Kesu; fortunately, Kesu is only hit in the arm. Indu, hearing the sounds of gunfire bursts into the room where she finds Omi sitting beside the remains of Dolly, stricken with guilt at having killed his wife. Indu recognizes the kamarbandh and she confesses that she was the one who stole the kamarbandh. Both Indu and Omi come to the understanding that they have been played for fools by the treacherous Langda. Indu slits Langda’s throat in outrage and a heartbroken Omi kills himself, leaving a wounded Kesu and broken Indu to look on at three corpses.
