The film begins with a group of villagers in Laalgaon engaged in a song while three Dalit girls are trapped in a school bus and are raped by a few men. Ayan Ranjan (Ayushmann Khurrana), a St. Stephens College graduate and an Indian Police Service officer, is recently posted to Laalgaon as the deputy-Chief of district police and is warmly welcomed by officers Bhramadatt Singh (Manoj Pahwa) and Jatav (Kumud Mishra). He is introduced to the caste discrimination the village faces when he stops to buy a bottle of water from a local shop to which an officer tells him that they are not allowed to have their water as the shop belongs to people belonging to a lower caste. He faces a similar situation at his welcome party where he is given a fresh plate to eat while trying to eat from Jatav’s plate. The very next day, it is shown that the two girls who were raped in the bus have been hanged from a tree, while the third girl Pooja is still missing.
During the post-mortem examination of the bodies, Dr. Malti Ram (Ronjini Chakraborty) finds out that the girls were gang raped, but is coaxed by Bhramadutt to not only delay the report but also to write that the girls were murdered and not raped so that the case becomes that of honour killing. Meanwhile, Jatav and his men are threatened and their jeep burned by Nishaad’s (a revolutionary) gang in order to get speedy justice. On seeing this, Ayan realises the gravity of the situation and decides to dig deeper in this case until the victims gets justice. On the other hand, Bhramadutt is trying to close the case at the earliest and persuades Ayan to do so as well on the pretext that the case is false. It is only when Gaura (Sayani Gupta), a relative of the girls informs him that they used to work for a local builder named Anshu Naharia and had recently asked for an increase in their salary by just Rs. 3 that the investigation gets more serious. Ayan decides to call Anshu for inquiry even though Bhramadutt persuades him not to do so. During interrogation Anshul says that the girls were punished so that the entire caste would be reminded of their status. On asking them about their status, he replies, “Their status is what we give them”. This deeply disturbs Ayan as he gets to see the loopholes behind the political system. He promptly decides to “un-mess” the mess and the very next morning, he puts the Article 15 of the Indian Constitution on the billboard as a reminder to all the police officers to first and foremost be Indians and that any kind of caste discrimination is a criminal offence. What happens next forms the crux of the story.