Omkara "Omi" Shukla is an enforcer for a gang that commits political crimes for the local politician Tiwari Bhaisaab. Ishwar "Langda" Tyagi and Keshav "Kesu Firangi" Upadhyay are his closest lieutenants. Langda gatecrashes a baraat and challenges Rajju, the groom, to try and stop Omkara from abducting the bride, Dolly Mishra. Rajju fails and the wedding never takes place.
Dolly's father, advocate Raghunath Mishra, is enraged with Omkara and at one point threatens to kill him. To sort out the misunderstanding, Bhaisaab arranges for Dolly to appear before her father; she clarifies that she eloped with Omkara and was not abducted. Her father remains disgusted and scared that she is in love with a man from a lower caste as well as a violent criminal and leaves the village in shame.
Omkara and his gang compromise Indore Singh, an electoral rival of Bhaisaab, by exploiting an MMS sex scandal; they also kill several of Singh's enforcers, while allowing one of them, Kichlu, to live. Bhaisaab is elected for parliament and Omkara is promoted to the candidate for the upcoming state elections.
Omkara appoints Kesu over Langda as his successor once he enters politics himself, as he feels Kesu, who hails from the upper classes and is college-educated, stands a better chance of winning over the younger, educated voting crowd than Langda, who is rustic and dropped out of school.
Langda, disappointed with Omkara's poor judgment and jealous of Kesu, his younger, less-experienced superior, decides to take revenge. He first causes a violent brawl between Kesu and Rajju by taking advantage of Kesu's low threshold for alcohol, which damages Omkara's faith in Kesu. Langda has Kesu convince Dolly to mollify Omkara, but at the same time uses Kesu's visits to Dolly as evidence to suggest to Omkara that the two of them are having an affair. Langda additionally has Indu, his wife and Omkara's sister, steal an expensive piece of jewelry that Omkara gifted to Dolly, and encourages Kesu to gift it to his girlfriend Billo.
Billo is later used to lure Kichlu out of hiding, so Omkara's gang can assassinate him. Omkara, Langda and their associates arrive at the hideout, where Billo is dancing. Omkara then chases down and murders Kichlu in a rage. Later, after they kill several people on a train, Omkara beats Langda and demands that he unambiguously tell him whether Kesu and Dolly are having an affair. Langda insists that they are.
On the wedding day, a bird drops a snake into paint being used by Dolly: a bad omen. Indu tells her brother not to marry Dolly if he has any doubts. Omkara is still unsure, and demands proof from Langda. Later, Langda tricks Omkara into believing that Kesu's explicit talk about Billo is referring to Dolly, and arranges for Omkara to watch Billo drop Omkara's heirloom jewelry at Kesu's door.
Convinced of the affair, Omkara smothers Dolly to death on their wedding night. Elsewhere, Langda shoots Kesu, who collapses but survives. Rajju shoots himself. Hearing gunfire, Indu rushes to Omkara, where she finds Dolly's corpse and the recovered jewelry. She confesses to having stolen the jewelry for Langda, making Omkara realize that Langda is responsible for his fatal misunderstanding. As Langda leaves, Indu slashes his throat in retribution. The wounded Kesu enters, asking Omkara "How did you ever think...?" Omkara shoots himself in the chest and dies next to his wife.
