1980: A low-level party cadre Sengalvarayan was dedicated to his regional leader Tamizhvanan and party, to the extent that he is working for a party meeting when his wife goes into labour. Accidentally, Tamizhvanan comes to the area of Sengalvarayan's house, and lends his car to take Sengalvarayan's wife to the labour ward, but the delivery happens safely inside the car.

1996: Sengalvarayan's son Pazhani secures the first rank in his 10th standard state exam, and visits Tamizhvanan, 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 an accidental murder of a rebel in the party, by Tamizhvanan due to caste-related comments by the rebel on him. When Tamizhvanan 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 prison, citing the leniency of juvenile laws in exchange for an MLA seat for his father in the upcoming by-elections. Tamizhvanan accepts and Sengalvarayan later becomes an MLA.

2015: Trainee IPS officers Mithran, Shakthi, Suraj, Kathiresan and Janardhan 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 they are aware of their discreet activities. In the evening, they go out to meet that person who is revealed to be forensic pathologist and Mithran ex-girlfriend Mahima. 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. 4 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 crime network, who bend the law for their own financial benefits. He singles out three influential persons: pharmaceutical mogul Ashok Pandian, mineral magnate Charles Chelladurai and chieftain Perumal Swamy. 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. Siddharth uses the medical field for the wrong reasons and for his own profit. Sengalvarayan is now the incumbent Health Minister in the minority government headed by Tamizhvanan, who is now the CM. 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 Mithran is recovering from the gunshot wound in the hospital, an electronic bug (GPS + audio transmitter) is implanted during surgery by Siddharth. Through the bug, Siddharth listens to all of Mithran's plans and continuously monitors his whereabouts and conversations via audio transmission. Then comes evidence against Siddharth in the form of Manimekalai. Manimekalai 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 hires goons and kill her. But before being killed, she records a video and stores it in an SD card so that someone will find it.

Before Mithran can find the card, Siddharth finds out and assigns Vicky, Perumal Swamy's brother, 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 that 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 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 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 Tamizhvanan. When Siddharth learns about this, he asks Sengalvarayan to pretend to have chest pains and move outside to the hospital. The ruling party forces Sengalvarayan either to resign within 24 hours or he will be dismissed. Mithran appeals to Tamizhvanan that he has evidence and wants to arrest Siddharth, and he is granted permission to do so. Hence Siddarth kills Sengalvarayan using his goons in an accident and forces Tamizhvanan to stop actions against him, or he will lie that Tamizhvanan killed his father for personal vengeance. However, the next day at Sengalvarayan's state funeral, Mithran arrests him on Tamizhvanan'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 pushes him and learns that Siddharth did not wore the vest and is fatally shot by Shilpa. Before dying, Siddharth 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. Siddharth's accomplices are arrested and the film ends with marriage of Mahima and Mithran.