Amar, the head of a black-ops team, is summoned by Police Chief Jose to bring justice to a group of masked vigilantes, who have killed Stephen Raj (following his arrest and subsequent release after being busted for helping Adaikalam and Anbu in Kaithi), ACP Prabhanjan and his foster father, Karnan. Amar leads the investigation by digging into Karnan's life, as his murder seems out of place, since Karnan was a common man and the other two were higher officials in the Narcotics division. He learns about Karnan's recent addictions to alcohol, drugs and prostitutes, while at the same time being very protective of his infant foster grandson. While investigating, Amar about two missing containers of drugs being hunted by Sandhanam, who runs a much bigger drug syndicate than Adaikalam, named Vetti Vagaiyara. The two containers had to be delivered to his cold-blooded smuggler boss 'Rolex', whose identity is unknown. If the drugs are delivered, Rolex will help Sandhanam form his own government; if not, Sandhanam and his family will be killed.

Amar slowly figures that all of Karnan's addictions were a ruse to cover up a highly covert operation being run by him. Meanwhile, Veerapandian, a PWD officer, assigns a meeting with other gangsters at a theatre, where he reveals that he, along with a contractor named Rudra Pratap, know the location of the drug containers as they want to bring the containers to Rolex, bypassing Sandhanam in the process. However, the masked vigilantes arrive and kill Veerapandian. Amar and his team arrive at the scene through a tracking chip left behind by Karnan and successfully capture one of them, revealed to be ex-Inspector Bejoy. Amar interrogates Bejoy, who reveals that his family was killed for his role in leading the earlier drug bust, leading him to don the mask and join the vigilantes. Realizing that Rudra Pratap is also a target of the members, Amar and his team sneak into Rudra Pratap's daughter's wedding ceremony, where Rudra Pratap has also invited Sandhanam for protection, fearing for his life and family. The masked men, along with their leader, arrive at Rudra Pratap's daughter's wedding, where the leader threatens Rudra Pratap by holding his daughter at knifepoint. The leader drags Rudra Pratap, and escapes from the wedding on a bike, leaving the other members to deal with Sandhanam. However, Sandhanam manages to defeat all of them. Amar chases the leader and finally confronts him.

The leader makes a video call to Sandhanam and reveals himself to be Karnan, who is actually alive and had faked his death. Karnan kills Rudra Pratap and escapes from the police. Amar reveals that Karnan is actually Vikram, who was the former commander of the black-ops squad's pilot batch. Vikram's team, consisting of 12 members, was disbanded after a botched mission in 1991 and its members were declared as terrorists. Subsequently, them and their families were hunted down but Vikram and three other members of the team managed to survive.

Amar meets up with Jose and figures out that Jose himself is Sandhanam's mole in the department. It is revealed that Prabhanjan was captured by Sandhanam with Jose's help. Sandhanam had interrogated Prabhanjan about the containers and upon Prabhanjan's refusal to divulge any information, murders him. Enraged, Sandhanam killed him, which forces Jose, Veerapandian and Rudra Pratap to cover up the murder by making it look like a terrorist attack. Amar orchestrates a bomb blast at Sandhanam's house, which destroys his bungalow and his drug lab in the basement. Jose informs Sandhanam in the nick of time and everyone but Sandhanam's brother Elango manage to escape the blast. Jose reveals Vikram's and Amar's identity to Sandhanam. Later, Vikram arrives at the prison and frees Bejoy and his team. Sandhanam brutally kills Amar's wife Gayathri by decapitating her and sends his men to attack and kill Vikram's daughter-in-law and grandson at Prabhanjan's house. Having deduced this, Vikram rushes to save them, where a team member of Vikram's Pilot Black squad and associate, Agent Tina, who was undercover as the domestic help of the house under the name Valliamma, is killed whilst protecting Vikram's daughter-in-law and grandson.

Vikram finally manages to save them. Distraught at Gayathri's death, Amar joins Vikram's gang to take down Sandhanam and his syndicate. He leaves for Jose's house and kills him after learning about his involvement in Gayathri's murder. It is revealed that the reason for Vikram's actions is not vengeance, but a drive to bust the drug syndicate in the city, which manifested in him through Prabhanjan's death. He also admits that Prabhanjan was his own biological son. Vikram and his grandson reach Chennai Port where the containers are hidden. Sandhanam learns about the location of the containers and attacks Vikram. Vikram mows down Sandhanam's men with a cannon and M2 Browning but the remaining members of his Pilot Black squad, Agents Uppiliappan and Lawrence are also killed in the action whilst trying to protect Vikram's grandson. Vikram blows up Sandhanam's containers and Sandhanam is killed in the ensuing blast. Amar mourns Gayathri's death and with the syndicate destroyed, he dons the grease paint to continue Vikram's mission, by joining his team, along with Bejoy.

In Sassoon Docks, Mumbai, Anbu and Adaikalam, arrive with their men. They meet up with the gangsters affiliated with Sandhanam and hold a meeting with their boss, Rolex. Adaikalam and Anbu reveal Dilli's involvement in the drug ambush, and Sandhanam's men reveal Vikram and Amar's involvement in destroying their drug syndicate and killing their leader. Rolex announces a huge sum as a reward for the execution of Amar, Dilli, and Vikram's team. They also reveal the current location of Dilli, in Bundelkhand, Uttar Pradesh, and Vikram's family in San Francisco. However, unknown to Rolex and everybody else at the meeting, Vikram is hiding amongst the gangsters and learns about the bounty placed on his team and Dilli.