The film is based on the 26th Dec 2004 Tsunami that hit Southern part of India. The story is set in the week before the catastrophe.
Govindarajan Ramaswamy, or Govind (Kamal Hassan), is a biotechnologist working at a lab in California. His team has invented a deadly virus which has the potential to be the greatest bio-weapon ever made by man, with the actual matter being kept well protected. However Govind soon finds the devastating effect of the virus and wants to destroy it. But his boss, Dr. Sethu (Rajesh Toleti) attempts to sell it to terrorist organizations. Upon the discovery of this, Govind makes off with the vial containing the virus and flees through the city and eventually the vial lands in India, through some courier company. Govind follows the vial. Govind is followed by Christian Fletcher (Kamal Haasan), who is an ex-CIA officer, also appears in the scene wanting the vial for his own nefarious purposes.
Receiving intelligence on this issue, Fletcher decides to fly to India to recover the vial. Prior to leaving, he finds himself a translator in the Las Vegas pole dancer, Jasmine (Mallika Sherawat
In Japan, Shingen Narahashi (Kamal Haasan), a Japanese martial arts expert and brother of Yuka, (Govind’s colleague’s wife, who Fletcher had killed) thinks it was Govind who killed his sister and comes to India, seeking revenge.
Upon arrival at Chennai airport, the vial is transfered to another plane and Telugu intelligence officer, Balram Naidu (Kamal Haasan, again) intervenes and questions Govind, who insists on talking to higher authorities but to no avail.
Fletcher and Jasmine pursue Govind to Chidambaram wherethe vial, is delivered to a 95-year-old, mentally retarded woman, Krishnaveni (Kamal Haasan, again again), who lives in belief of receiving a parcel from her son, who perished in 1953. Govind tries to rescue the vial from her grand-daughter Andaal (Asin Thottumkal). Asin thinks Govind is a terrorist and tries to warn the police, thus enabling Fletcher to catch Govind on many occasions in a cat and mouse chase.
A few more characters (all played by Kamal Hassan, which makes the total 10) are introduced and finally Fletcher gets hold of the vial. How will he bring destruction to society?
The film connects the present to an event of the 12th Century and talks about the Chaos theory and Butterfly effect.