Soon-to-be-released convicts Raja and Babu meet Manohar, who is on death row. He tells them his sister Sumathi was kidnapped by a taxi driver and taken to Muthuraaj, a playboy who raped and killed her. Muthuraaj murdered the taxi driver and framed Manohar with his elder brother Rajamanickam, ally Jayaram and a corrupt police inspector Nallasivam. Raja and Babu believe Manohar; Raja stalls his execution by fracturing his left arm. Once released, the two men initiate an elaborate plan.

Posing as CBI officers, Raja and Babu conduct a fake income tax raid in Nallasivam's house in his absence. They discover he has an abundance of illegally earned wealth, and force his wife Kalyani to sign a paper confirming this. Nallasivam learns about the "raid" in his house and threatens to arrest Raja and Babu, but they gain leverage over him, having created numerous copies of the paper.

Raja later falls in love with Geetha, another police inspector. He tells Babu to "romance" Rajamanickam's daughter Chithra as part of the plan, but it backfires. Raja discovers that Geetha is Nallasivam's daughter and lies to her about being a CBI officer. Raja blackmails Nallasivam into helping him infiltrate Muthuraaj's services as a new bodyguard. Babu later genuinely falls in love with Chithra, who reciprocates. Though Raja soon reveals to Geetha the truth about himself and Nallasivam's corrupt nature, she accepts him.

Pressured by Raja, Nallasivam introduces Babu to Rajamanickam as a millionaire in love with Chithra; Rajamanickam arranges their marriage. During the ceremony, Babu tells Rajamanickam he knows of the group's crimes and says he will only marry Chithra if the group confess in writing. When Rajamanickam refuses, Babu reveals his true identity and cancels the marriage, telling Chithra her father refused to give him the requested dowry. Rajamanickam, Jayaram and Muthuraaj realise that Nallasivam lied to them, and Babu is helping Manohar. They plan revenge.

For over 20 years, Rajamanickam has been trying to uncover a secret that is only known to Kandhasamy, Manohar's father, held captive in his basement. Kandhasamy has amnesia so a rope is used to jolt his memory. It succeeds but Kandhasamy refuses to tell Rajamanickam. Jayaram believes Kandhasamy will only tell Babu because he is helping Manohar. Babu, now their prisoner, is taken to the basement. Raja follows to watch over Babu, and they secretly rescue Kandhasamy and his wife Padma and escape.

While conversing with Padma, Raja realises he is Kandhasamy's first son who went missing years ago during a school trip. Babu identifies Kandhasamy as the murderer of his parents and has a fight with Raja. Kandhasamy stops their fight and reveals the truth: he had learned the location of a treasure cave, but wanted to tell only IG Sriram. Rajamanickam imprisoned Kandhasamy and his family to seek the location, but he refused. Rajamanickam then murdered Sriram and his wife disguised as Kandhasamy, sparing their son Babu so that he could blame him. The family escaped, and Padma reveals that they were recaptured after Manohar's arrest before being rescued by Raja and Babu. On learning the truth, Raja and Babu reunite and swear revenge.

Geetha and Chithra join Raja and Babu in their plan to avenge. Rajamanickam meets Raja and Babu, and at the instigation of Jayaram, agrees to sign a paper incriminating Muthuraaj in exchange for the location to the cave, which will be the "dowry" for Chithra and Babu's marriage. Chithra records Rajamanickam and Jayaram's conversation on tape; she gives it to Muthuraaj, who plans revenge along with Nallasivam.

Kandhasamy, Rajamanickam, Jayaram, Babu and Raja reach the cave and find many gold bars. Rajamanickam signs the paper as promised, but Raja and Babu intend to have him arrested for his crimes. Soon after, Muthuraaj and Nallasivam arrive and create chaos with thugs and bombs; Rajamanickam and Jayaram are killed while Raja, Babu and Kandhasamy escape. Muthuraaj and Nallasivam drive away with many gold bars but are stopped by Raja and Babu, and arrested by Geetha. Manohar, now fully healed, is exonerated.