The film starts with Krishna (Vikram ) collapsing onto the road and lying there at night as traffic passes him by. Krishna is constantly murmuring the name Nila and asks everyone where she is. Many incidents forces him and takes him to court.There, Vinod (Santhanam) confronts Krishna thinking that he is rich and tells Krishna that his boss/colleague Anuradha Ragunathan a.k.a Anu (Anushka Shetty) will represent him.Intially being little hesisitent,Atlast she says yes,after knowing his pathetic situation. Anu meets Krishna's friend Victor (Krishna Kumar) and they are told Krishna's story.

Krishna lives in a small village and works in a chocolate factory as a helper and it is owned by Victor who is extremely kind towards him. Other workers who are also slightly mentally unstable work there too and it is managed by Murthy (M. S. Bhaskar). One day Krishna announces to everyone that he is going to have a baby . On the way he buys new things for the baby and mother but as he arrives he is drawn to the baby and is informed by the doctor that Bhanumathi, his wife has left and gone to God. Krishna who is unable to understand exactly what has happened to Bhanu takes the baby home but does not know what to do and where to start. Raji,Murthy's wife teaches Krishna how he has to take care of his baby and he is shown nurturing her and bringing her up with so much love. He ends up naming the baby girl Nila after seeing the Nila (moon).Nila (Baby Sarah) grows up and at the age of five she is entered into a school with the help of Victor and Krishna's friends. Krishna is initially hesitant to be apart from her and Nila is told that she needs to go to school, study hard and become a doctor so she can take care of her dad.

Nila then casually meets the school correspondent Shwetha Sargunam (Amala Paul) and Shwetha immediately takes a liking to Nila and finds out that her mother is dead. Nila is then told by her teacher that school correspondent has organised a competition and at the end of the competition, Shwetha goes to congratulate Nila with her fiance Karthik (Karthik Kumar) but is shocked when she sees that Krishna is Nila's dad. Murthy tells Shwetha that it was Krishna's neglect and irresponsility that killed his wife Bhanumathi and that Krishna will do the same to Nila.Shwetha runs of crying and holds back Nila and says that she will not allow her to return with Krishna.

After a long love struggle between Krishna and Nila,a car pulls up blocking Krishna's path and Shwetha's father, Sargunam gets down and tells them to behave themselves and apologizes to Krishna. He also reveals that Bhanumathi is his daughter and is Shwetha's sister. She had left her family to marry Krishna as they didn't approve but they are now shocked to learn that she died at childbirth. Sargunam asks Victor and the entire village to allow him to take Krishna and Nila with him and that he wants to take care of them as they are the only people left that remind him of Bhanumathi. Everyone agrees and Krishna and Nila leave with Shwetha's father. However about 30 km from Chennai in the middle of nowhere Krishna is tricked and told to get out the car and they drive off with Nila abandoning him. This leads to the very first scene of the movie as Krishna chases after the car.

Anu and Vinod upon hearing the story vow to help Krishna and go to see his father in law. However he claims to not know anyone called Krishna or Nila and throws them both out of the house. Anu decides to file a petition at the court and legally asks that Nila is brought to court. Sargunam hires the best lawyer available Bashyam (Nassar) who never loses a case,against Anu.

Does Krishna and Anu succeed to get back Nila or not is the rest of the story.