A low-level party cadre Sengalvarayan (Thambi Ramaiah) is dedicated to his leader and party.He and his son Pazhani who secures the first rank in his 10th standard state exam,visits the party deputy-leader, now the chairman of the party and a member of the ruling coalition for his blessings with his father. While they are waiting in the party office for the leader to come in, they witness a murder of a rebel party candidate by their own revered leader due to caste-related comments by the rebel on him. When the leader asks Sengalvarayan to take the blame by saying that he killed the man due to rage about the rebel’s comments, Pazhani volunteers to take the blame and is willing to go to jail, citing the leniency of juvenile laws in exchange for an MLA seat for his father in the upcoming by-election.
15 years later, trainee IPS officers Mithran, Shakthi, Suraj, Kathiresan and Janardhan “Jana”, discreetly assist the police in catching a gang which kidnapped four girls. One day Mithran receives a cryptic text message on his phone from an anonymous number stating that he/she is aware of their discreet activities. In the evening, they go out to meet that person who is revealed to be Mahima (Nayantara), who loves Mithran. Later that same night they happen to witness the murder of a man named Ramar who is a social activist with the pretense of snatch theft. Mithran and his friend catch the gang and their leader and hand them over to the police; however, four days later the leader of the gang comes to the IPS headquarters with the home minister. This political and organised crime comes as a shock to Mithran and his friends. Mithran takes them to his house and shows his research on connecting all small unrelated incidents into the global view of a hidden network of politicians, industrialists and criminals who bend the law for their own financial benefits. He singles out three prominent business oligarchs (a pharmaceutical mogul, a mineral magnate and a don). When he tries following one he realizes that all three of them work as a group and they all work for a wealthy and influential scientist Siddharth Abhimanyu. After the completion of his training, Mithran is awarded medals for specializing in dealing with organized crime during training and also for being the best probationer of the batch, and is posted as the ASP of the Organized Crime Unit.
Mithran discovers that Siddharth is Sengalvarayan’s son Pazhani. After his release from prison, Pazhani had his name changed and left India to complete his education abroad. After his graduation, he returned to India and is now a well-established scientist. Siddarth uses the medical field for the wrong reasons and his own profit. Sengalvarayan is now the incumbent health and welfare minister in the minority government headed by the party leader. At that time Angelina, a Swiss pharmaceutical company owner and activist tries to make generic medicines for life-threatening diseases available in India at low cost affordable by poor people. Siddharth’s assassin kills Angelina before she can sign the agreement document with the government and shoots Mithran at the same time. While he is recovering from the gunshot wound in the hospital, an electronic bug (GPS + audio transmitter) is implanted during surgery. Through the bug, Siddharth listens to all of Mithran’s plans and continuously monitors his whereabouts and whatever he talks via an audio transmission. Then comes evidence against Siddharth in the form of Manimekalai (Abhinaya). She was a scientist at Siddharth’s research lab, where a seaweed that can cure diabetes is found abundantly in the oceans. Siddharth tries to sell the technology and rights to extract medicine from the seaweed to multinational pharmaceutical companies but is opposed by Manimekalai. So Siddharth arranges goons and the goons rape and kill her. But before being killed, she records a video and stores it in an SD card so that someone will find it. But before Mithran can find the card, Siddharth finds out and assigns Vicky (Vamsi Krishna) to recover the card, but Mithran tells Jana to get the card. He successfully gets the card after a fight with Vicky, but through the bug, Siddharth knows this and kills Jana. Mithran comes back to his special house where he finds a pin has been changed in a picture which turns out to be the picture of Ananya who was Miss World 2011 and a close acquaintance of Siddharth whose girlfriend Shilpa (Mugdha Godse) was also part of that event. Mithran doubts whether Siddharth himself would have come to his house. Mahima checks the fingerprints on the pin keeping the gun case Mithran received from Siddharth in his posting ceremony and the fingerprints match. A flashback reveals that Siddharth killed Shilpa’s father so that she would not participate in the competition and as she will not have a ticket to go to her father’s funeral he offers to take her in his chartered flight and wins her over. Mithran frantically searches for the bug which he eventually finds out and removes.
Mithran captures Vicky and records all the information from him. He drugs Vicky and manipulates Siddharth into killing him. At the same time, Siddharth’s father reads the changed medical report, which contains very good medical contracts for public welfare and multiple accusations against the CM. When Siddharth learns about this, he asks Sengalvarayan to pretend to have chest pains and move outside to hospital. The ruling party forces Sengalvarayan either to resign within 24 hours or he will be dismissed. Mithran appeals to the CM that he has evidence and wants to arrest Siddharth, and he is granted permission to do so. Hence Siddarth kills his father using his goons in an accident and forces the CM to stop actions against him or he will lie that the CM killed his father for personal vengeance. But the next day at his father’s state funeral, Mithran arrests him on the CM’s orders.
When Siddharth is arrested, Mithran tells him that the medicine was patented in Manimekalai’s name (despite Siddarth being the inventor) and will be made as generic medicine instead of a patent-protected one. It is also revealed that Sengalvarayan is still alive, saved by Mithran and his gang and the public funeral held was for Jana. Mithran makes a deal that he would save Siddharth’s life for information and evidence on all of his criminal associates and activities and gives him a bulletproof vest to fake his death during his transport to the court.
They also plan to take down the setup planned by various VIPs to kill Siddharth when one of them gets close to Siddharth, Mithran notices and pushes Siddharth back. To Mithran’s surprise, Siddharth does not wear the vest and is fatally shot by Shilpa. Before dying, he tells Mithran that he hid all the evidence in an SD card in the bulletproof vest, adding that he had not done it for the nation but because Mithran had asked for it. The film then happily ends with the wedding of Mahima and Mithran. The last narration was narrated by Mithran on how he became a successful police officer in his life after solving the case (about a boy going to prison for a crime he committed) he read for the first time on the newspaper .