The story opens with a couple with twins sitting in a train. However, a thief snatches one of the sons, and after stealing the jewellery of the son, leaves the baby. However, the baby is found by a childless couple in a village. The couple hail from a large and powerful family, and they raise him as their son without telling him the truth. Thus, the twins grow up in different environment. The one living with the parents (Vasudevan a.k.a. Vasu) grows up in Chennai to become an officer in a private investigative agency. The other son, Vetrivel a.k.a. Vel grows up in Dindukkal and becomes a rustic young man.
Vasu manages to charm a journalist, Swathi (Asin), through his professional ethics. Their courtship occurs through a series of events where she initially mistakes him for a drug addict. Meanwhile, Vel is engaged in the bloody tussle with Sakara Pandi (Kalabhavan Mani), who has deep rooted enmity against the family. Sakara Pandi had killed Vel's adopted parents, which enrages Vel. Vasu is filled with smiles, while Vel lives with sickles and dangerous duels.
Vasu’s mother (Saranya) cannot forget her lost son. She is longing to bring him back home. However, all her efforts to search for him are in vain. The family with whom Vel lives love him a lot. Everyone, especially the grandmother (Lakshmi), are emotionally dependent on him and she is always scared that someone will come looking for him and take him away.
One day, while filming a documentary in Dindukkal, Swathi sees Vel in a gang fight. She immediately informs Vasu. Vasu goes to the village and meets his brother. The family refuses to send Vel back with him. Vasu, understanding their unadulterated affection towards Vel, agrees to give up his claim. He stays with them for a couple of days and realises that the family really loves Vel and cannot live without him.
However, while at the train station, Vasu has one request. He wants Vel to go to Chennai pretending to be him and live with his mother. Vasu, in turn, would behave as Vel in the village. Vel accepts the offer.
Vasu continues Vel’s struggle against the powerful Sakara Pandi, but with a different approach. Vasu uses his brain and investigating network instead of muscle power. The rules of the game change, and Sakara Pandi finds himself cornered. Vasu eventually overthrows Sakara Pandi, and the family is happy.
Vasu's parents find out that their long-lost son is well. Despite initial attempts to bring him back, they finally relent after seeing the grandmother cry for her grandson. They understand the pain of losing a child, and do not want anyone else to go through the same pain.