| Director | Shakti Soundar Rajan |
|---|
The opening scene shows a container of toxic liquid being spilt from a transport vehicle at a chemical laboratory in Ooty. A stray dog consumes it and turns violent, which then bites a security guard. The security guard turns into a zombie within hours and starts a chain of human infections via bites.
In the present, Karthik is a traffic police sub-inspector in Ooty who avoids all kinds of dangers while taking care of his younger sister Vidya, who is in her early teens. Both are orphans but live with Karthik's friend Chinnamalai, a traffic police constable. Karthik is in love with a cardiologist named Renuka aka Renu, but never proposes in all their meetings. Renu is engaged and is about to marry an NRI named Naveen, who is also a cardiologist. One day, Karthik messes up with Minister Gurumoorthy by allowing an auto carrying pregnant women in Gurumoorthy's way. The next morning, Karthik finds that Vidya has gone missing. While looking for her, he was suddenly attacked by zombies. At the same time, the police of Ooty is informed of the outbreak and is ordered to shoot anyone who has turned into a zombie. Karthik looks for Vidya by putting up posters of his missing sister on walls and killing zombies in his way. He receives a call telling him to arrive at a place to find his sister. There, he finds Renu and a group of doctors, including the chief doctor Dharan, all working to find a cure against the undead. At Renu's house, Karthik and Chinnamalai find Gurumoorthy, who is Renu's father, and learn that Gurumoorthy has kidnapped Vidya for vengeance. Karthik finds Vidhya at a swimming pool, surrounded by Gurumoorthy's zombified henchmen, and discovers that the zombies are hydrophobic. Renu tells Karthik to save the doctors trapped inside the house, which zombies have invaded.
Escorted by Karthik, the team comprising Dharan, Renu, another doctor Kamal, Gurumoorthy, Chinnamalai, and Vidya heads to Coimbatore, where they have to use medical equipment to find a cure to the tragedy. By this time, Dharan had already sustained a scratch from a zombie that had a delayed onset of infection; he chooses not to disclose it to anyone, fearing the consequences for his own safety. When they arrive near Mettuplayam, they unexpectedly discover that the infection has already spread to Coimbatore. The zombie crowd surrounds the police van, so Karthik is forced to drive rashly to kill the zombies one by one. Later, Gurumoorthy unknowingly disturbs some zombies, and Karthik ends up shooting them, which attracts the attention of a nearby zombie horde. They are all forced to take shelter in a mall opposite the hospital. Meanwhile, Naveen is inside the hospital trying to find a cure. They get hold of Shri, a frightened security guard of the mall.
After a few hours, Dharan turns into a zombie and bites Vidya. Karthik kills Dharan with his gun, but Vidya does not turn into a zombie even though she was attacked almost an hour ago. Kamal says she can help them find the vaccine as she has the required antibodies and immunity. Karthik has to escort them to the hospital, which faces the mall. For this, he uses pressurized water from the mall's fire truck, knowing that they are allergic to water. Despite the shorter time frame, Karthik manages to get everyone safely to the hospital except Renu. He goes back to the mall to bring Renu, but he does so without water. He leads Renu to the hospital but gets bitten by the zombies while escorting her. He himself slowly turns into a zombie, but he safely escorts her to the hospital before his human feelings are lost, and also advises Renu to shoot him. She is too adamant about knowing why he saved her, despite Naveen's uncaring attempts and her selfish father, and realizes his love for her, but Karthik turns into a zombie. Thus, Renu shoots him.
The doctors find the required antidote and start addressing the virus. Later, Karthik, now completely a zombie, is seen above a bus bound for Chennai, implying that Renu did not shoot him properly and he has survived the attack, possibly alluding to a sequel.