 Rajiv Gandhi was assassinated on 21 May 1991 in Sri Perumbatur, near the then Madras.The government of India constituted SIT a day later, and Major Sivaram (Mammootty) a top investigation officer and a NSG commando with a proven track record is put in charge to hunt down the killers.His bosses Partipan, the SIT chief and DIG Raju (Lalu Alex) give him all the necessary logical support with only one request- "Catch Sivarasan alive, before he consumes the deadly cyanide."