Conjoined twins Vimalan and Akhilan involve themselves in a series of deaths involving their father’s company. However, the truths that they initially uncover lead to a bigger conspiracy, one that spans across the globe.
Nandha (Nandha Durairaj) is an upright sub-inspector of police who has been transferred 15 times in three years. He is then transferred in a police station based in Pollachi. There, Police Inspector Pandian (Natarajan Subramaniam) is in the pay of Minister Periyannan (Rajagopalan), who runs in own government in the place. Nandha is shocked to note that Pandian and the entire police department are corrupt. Thereafter, Nandha tries hard to enforce the order. Soon, both policemen clash. Pandian becomes an honest policeman after Periyannan’s men attempt to kill him, and he is revived with blood transfusions from the public. However, Nandha does not believe that he has truly changed. After a fellow honest sub-inspector gets killed by Periyannan’s men, Nandha blames Pandian, and through short routes, becomes inspector himself. He arranges for Periyannan and his men to clash with Pandian, but in the ensuing fight, Pandian kills them all, while Nandha walks away.
Sitharam (Arjun) is a well respected auditor who lives with his PA Muthuswami (Anu Mohan) in Chennai. Although being a short-tempered and tensed person, Sitharam is very good at heart who helps the people in need. He soon meets and falls in love with Kalyani (Sonali Bendre). After a couple of meetings she too falls in love with him by seeing his good nature.
But Sitharam faces problems in the form of another loving couple, Akash (Suchindra) and Akhila (Ruchita) due to an argument between Akhila and Akash and Akhila acts as Sitaram’s fiancé so that she can get rid of Akash just before he proposes to Kalyani. Kalyani, being an innocent, believes her words and goes away from Sitharam. Hence, Sitharam becomes the main antagonist of the film to make the lives of Akash and Akhila the living hells.
Maasilamani aka Maasi (Nakul) is an orphan living in a lower middle class colony. With a heart of gold, he is a popular guy who takes up local issues, fights for them, and is considered a rowdy by those who do not know him. Enters the heroine Divya (Sunaina), a rich upper middle class girl who is a dance instructor and with whom Maasi falls in love at first sight. Divya shows aversion to his rowdyism and gets offended with his proposal. Maasi attempts to win her family by being a good person and dons another name, Mani. All are aware that Mani and Maasi are one person except Divya. When Divya finds out the truth, she gets into a dilemma as whom she has to choose. Bhoopathy (Pawan), the local corrupt sub-inspector who is also behind Divya, is determined to flop Maasi’s plans and prove Mani is Maasi. How Mani wins over Divya serves the climax of the movie.
Naachiyaar (Jyothika) is a tough policewoman in Chennai who is put in charge of solving an underage rape case. She tracks down a pregnant Arasi (Ivana), the victim, from her uncle and his goons who plan to get her an abortion. Although Naachiyaar saves Arasi, her uncle and his friends escape and go into hiding. Meanwhile, Naachiyaar’s partner, Feroz arrests the suspect, Kaathu (G.V. Prakash Kumar). He is then sent to a juvenile home, where he tells his story to one of the wardens, who is soft-hearted towards him.
Through flashbacks, we see how Kaathu and Arasi first met. Both are still teenagers from the slums but they do not go to school but are forced to work to help support their respective families. Arasi works as a maid at wealthy families’ homes while Kaathu does odd jobs for a living. One day, while her employers are away, Arasi invites Kaathu into the house where they (impulsively) make love. However, Arasi quickly regrets and pushes Kaathu away, who leaves upset.
Krishnasamy (Arjun Sarja), a respected man, and Samiyappan (Thilakan) are in a feud for several years. Amudha (Nikitha), Krishnasamy’s daughter, hates her father because she thinks that he is a killer.
A few years before, Krishnasamy was a tea master with his friend Kandhasamy (Goundamani). After his father’s death, Krishnasamy had a lot of responsibility. He fell in love with Sindhamani (Roja). In the meantime, Samiyappan, a local don, cancelled his engagement because Sindhamani’s father promised Sindhamani to his son (Raja). One day, Krishnasamy ridiculed Samiyappan in a politic function. This humiliation irks Samiyappan, so his henchmen burnt Krishnasamy’s house and Krishnasamy’s brother who was in the house died. In anger, Krishnasamy entered Samiyappan’s house and fought against his henchmen but an honest police officer (Nagesh) arrested him before he committed murder. The police officer gave him a mission: stopping Samiyappan’s illegal activities.
Maaran, a sincere doctor who fights against corruption and Vettri a magician who is out for a revenge. Both of them are estranged brothers and once they come together, they get to know about their common enemy, Daniel, who had killed their father and mother.