The Plot opens with a stray dog becoming a violent Alien-like creature, after drinking toxic fumes washed out by a scientific laborarory in Ooty, which then bites a security guard. The security guard turns into a zombie momentarily and starts a chain of human infections via bites.
Back to the present, Karthik (Jayam Ravi) is a Traffic Police Officer in Ooty who avoids all kinds of dangers as he takes care of his younger sister Vidhya (Anikha Surendran), who is in her early teens. Both are orphans but they live with Karthik's Comic Constable Friend Chinnamalai (Kaali Venkat). He is in love with a doctor named Renuka (Lakshmi Menon) but never proposes in all their meetings. Renu is engaged and is about to get married to an NRI named Naveen (Amit Bhargav), who is also Cardiologist. Meanwhile, Karthik's sister is kidnapped and is suspected to be attacked by the zombies. The police of Ooty decides to shoot the people who have turned into zombies. Karthik is also looking for his sister and also kills some zombies. He receives a call in which he is told to arrive at a place to find his sister. There he finds Renu and her group of doctors, including the chief doctor Dharan (Jeeva Ravi) finding a vaccine. Karthik also finds his sister and later comes to know that the doctors are trapped inside the house which is invaded by zombies.