Anu is a college student; her fellow student Sasi desperately tries to win her affection. Sasi and Anu play various pranks on each other. Anu eventually admits her affection for Sasi and they begin a courtship. All seems to be well, but Anu is strangely sad from time to time; she repeats to Sasi that she senses an imminent danger to their relationship, but she is unable to pinpoint what the threat is or describe why it may materialise soon.
Anu begins to get frequent sharp headaches. Her father, S. P. Balasubramaniam as A. R. Rangaraj (ARR) tries to help her, but is not able to get to the bottom of the matter. ARR is a gentle old man who has devoted most of his life to his daughter. On her 18th birthday, Anu visits her doctor who determines that she has bilateral renal artery stenosis and is almost certain to succumb within a year. She may require an operation within that time, but the likelihood of her coming through it alive is minimal.
Anu asks the doctor to keep her illness a secret between them. Unknown to Anu, her father accidentally discovers it when the local pharmacist sends some prescription drugs through him. When Anu discusses the matter with Sasi, he expresses his support despite his grave sadness out of his love for her. Anu reveals a thread from her past that may explain her melancholic mood.
The film flashes back to several years before, when ARR had a happy family. Anu, then five or six, attended school; ARR worked and his wife managed the home. When ARR lost his wife to an illness, Anu took this particularly hard. ARR tried to help her cope with it and move on. Later, ARR met Sarada at a wedding. When ARR sought a tutor for Anu, Sarada took the position. The friendship evolved into a courtship, and ARR was about to propose marriage.
As time went on, Sarada realised her own responsibilities. Both her parents were deaf-mute, and she was the only way they could communicate with others; this left her torn between her filial duty and her personal aspirations. Things worsened when Anu missed her mother and was unable to accept Sarada (or anyone else) as a replacement. Sarada was bewildered and ultimately frustrated by all this. Despite ARR's assurances that they could work it out, she refused his proposal and decided to move to another city; her parents committed suicide as they felt they were a hindrance to their daughter. Since then, Anu has been plagued by guilt for her part in the breakup.
The doctors schedule the surgery. Anu takes this with stoic grief, and asks Sasi for one last thing: to find Sarada and attempt to reunite her with ARR. They find an old picture of Sarada, and Sasi recognises her as a woman he had met in Bangalore a few weeks ago. He sets off on a frantic hunt for Sarada. On the day of the operation, Sarada happens to be in Chennai en route to a training event in the United States. After a series of near-misses, Sasi locates her in the nick of time and brings her to Anu and ARR moments before Anu gets anaesthetised. Anu later goes for one last ride with Sasi on his motorbike and, right before they leave, she says that she has gained faith in surviving the surgery.
