Article 15 is the tale of an honorable police officer trying to unravel a caste-related offense. Delhi based IPS officer Ayan Ranjan (Ayushmann Khurrana) has been transferred to a village Lalgaon in Uttar Pradesh as a penalty posting. He comes to know immediately after joining the duty about a case linking three absent girls from the Dalit community in the village. The police out there don’t consider the issue, citing that the case isn’t grave and the community often records false protest. Things got intense when the corpses of two of the missing girls – Mamta – Shalu is found hanging on a tree.

The third girl Pooja was still missing. A local girl Gaura (Sayani Gupta) tells Ayan that these missing girls were used to work on 25 per day under the local contractor Anshu. When the girls demanded an increment of just 3 but it was discarded by Anshu. Consequently, they protested and left the job. Gaura claimed that Anshu may be sullied the girls to taught them a lesson.

Ayan took the case and started investigating the case as he grasped that Gaura is indeed true. But the black sheep in police department Officer Brahmdutt Singh (Manoj Pahwa) working under Ayan, furtively tries to modify the story of the offense. A story was released in the newspaper that their fathers killed them because both girls were in a same-sex relationship. The newspaper story claimed it was an honor killing, not a caste-related crime. Brahmdutt Singh also put pressure on Dr. Malti Ram (Ronjini Chakraborty) to modify the post mortem report according to the newspaper story. But the post mortem was Mamta and Shalu had been frequently gang-raped and then killed.

Ayan took all these challenges and dare to solve the case and find Pooja.