Set in the backdrop of the mystical city of Varanasi, Asur follows Nikhil Nair, a forensic-expert-turned-teacher, who returns to his roots at the Central Bureau of Investigation, and along with his former mentor Dhananjay Rajpoot, finds himself caught in a cat-and-mouse game with a brutal serial killer. What follows is a blend of suspense, mythology and the murders of some people totally unrelated.