A couple (Saranya Ponvannan and Charan Raj) travel in a train to Chennai along with their twin babies. During the journey, a robber in the train kidnaps one of the babies and gets down from the train. He steals the jewels and leaves the baby in a garden and runs away. Saranya and Charan Raj lodge a complaint with the police. The kidnapped baby is found by Nassar and Ambika and they adopt and raise the baby as theirs.
27 years pass by, Vasudevan aka Vasu (Suriya) works for a private detective agency in Chennai and lives with his parents Saranya and Charan Raj, while the kidnapped baby is grown into Vetrivel aka Vel (also Suriya) in a village named Chokkampatti near Dindigul. Vel’s family is widely respected in their village for their good deeds and is also responsible for protecting the villagers from the local politician and goon Sakkarapandi (Kalabhavan Mani). Sakkarapandi killed Vel’s parents years ago and wants to revenge by killing other members in the family also. But Vel takes the responsibility of protecting his family members. Meanwhile, Saranya and Charan Raj keep worrying for years about the fate of the lost child.
Vasu falls in love with Swathi (Asin), a TV anchor. They both decide to get married. Swathi, during a visit to Dindigul for a TV show, sees Vel involving in a local clash and informs Vasu. Now Vasu suspects that it might be his twin brother and decides to leave to the village to get more information. Appatha (Lakshmi) is the grandmother of Vel and she always fears that someday Vel’s biological parents will find him and take him away from them. To her shock, Vasu goes to Vel’s home and meets him. He informs about all the incidents and wants him to come back with him to Chennai and meet his parents. Vel gets shocked knowing about his past, but neglects saying that he cannot leave his adopted family and he prefers to stay with them in Dindigul.
Vasu requests Vel to permit him stay with for a week in Dindigul along with Vel’s family. Vel agrees and Vasu becomes close with the family members. Also Vasu gets to know about Sakkarapandi and his thirst for revenge on Vel’s family. A flashback is told by Kuzhandaivelu (Vadivelu) where Nassar finds about Sakkarapandi’s illegal businesses which made him lose his MP post and he also gets jailed. Sakkarapandi, after getting released from jail, poisons Nassar and Ambika. He also wants Vel’s entire family to be dead. Now Vasu plans to send his brother Vel to Chennai. He requests Vel to visit his biological parents disguised as Vasu and stay there for a few days, so that he will get to know his mother’s love towards him. Vel agrees hesitatingly.
Vasu wants his brother to lead a peaceful life free from sickles and fights. So he plans to trap Sakkarapandi strategically rather than physical attack. Vasu brings a team of investigative officers from his detective agency and asks them to closely monitor Sankarapandi’s moves and also to gather his family details. Meanwhile Vel meets his parents Saranya and Charan Raj in Chennai and stays with them without revealing his true identity. But Swathi’s relatives plan for a ring exchange ceremony between Vel and Swathi mistaking him as Vasu. Vel discloses to his parents that he is the elder son lost years back which surprises his parents.
Vasu calls Swathi to assist him whereby Swathi is sent to Sakkarapandi’s house to interview his wife (Aishwarya) thereby searching for some evidence against Sakkarapandi. Sakkarapandi’s college is sealed for selling drugs to students, and Vasu also gets evidence of Sakkarapandi frequently visiting the nearby forest for hunting wild animals. Sakkapandi gets arrested by police. To revenge, Sakkarapandi poisons the food provided for Appatha. However, she is saved by Vasu. Knowing this, Vel rushes from Chennai to Dindigul to meet Appatha. Now Vel’s family comes to know that it was Vasu in disguise of Vel which angers them. They scold Vasu and ask him to leave the place immediately. Vasu leaves along with Swathi.
Sakkarapandi plants a bomb in his sugar factory and plans to kill all the villagers who are working in his factory, thereby planning to create a chaos in the town. But Vasu and Vel get to know about his plans and they fight together against Sakkarapandi following which Sakkarapandi’s leg accidentally gets stuck between railway tracks. Vel amputates his leg to save the train, however Sakkarapandi dies due to the explosion of the bomb carried by him.
Vasu informs to his mother that let her allow Vel to stay in Dindigul itself as the entire family will feel the pain of losing a son who was raised for 27 years by them. Saranya understands and says that she is happy that her both the sons are leading a very good life and also she does not want to hurt the entire family by taking away Vel with them. Finally Vel stays with his adopted family in Dindigul while Vasu and Swathi get united.