After having killed the notorious extortionist Mayil Vaaganam in the first film, Duraisingam (Suriya) has gone undercover after meeting the Home Minister (Vijayakumar) and is working as an NCC officer in a school in Thoothukudi. The only people who know about this operation are the Chief Minister and Home Minister apart from himself. Sathya (Hansika Motwani) is a student who falls for Singam though he is waiting to marry Kavya (Anushka Shetty), his love interest. Susai (Santhanam), a local who works in the same school shows Singam parts of Thoothukudi and also tells him about the rogue elements dominating the area helping him in his surveillance. He requests the Home Minister to transfer Erimalai (Vivek) and another cop for assisting him. Sathya's moves are frequently repulsed by Duraisingam who learns that Sathya is the niece of Thangaraj (Rahman). Bhai (Mukesh Rishi) and Thangaraj, are two criminals who control the area. Bhai and Thangaraj have connections with an international gangster and drug lord Danny (Danny Sapani). Meanwhile, Sathya learns that Kavya and Singam are strongly in love and distances herself from them.
Though they are partners in their smuggling business, they conceal their partnership to the outside world and pretend like arch rivals when they are out in the public. Singam overcomes the criminals, Singam arrests Thangaraj and locks him in jail. He also finds that Danny has escaped. After a moment, Singam gets a phone call from someone informed that Sathya is accidentally died, then he rushed to Thangaraj's house and there he sees the death of Sathya.
He further analyzes that Sathya was killed by someone who poisoned her. Meanwhile, Singam traced that Danny is in Africa to do drug business again. Singam got permission from the Home Minister to go to Africa to arrest Danny. Finally Singam arrests Danny locks him in the same cell from where Danny had escaped. Lastly, he goes on an undercover mission to track down Sathya's killer and get ready to marry Kavya.