Senguttuvan (Aadhi) and Elango (Daniel Annie Pope) are two small-time crooks who work for a local jewel smuggler named "Nochukuppam" Ramdoss (Ramdoss). Senguttavan is attracted to a young woman Chanakya (Nikki Galrani) whom he sees every morning at the bus stop, however he never manages to speak to her. Chanakya eventually gets married, but her husband doesn't treat her well and physically and verbally abuses her in public.

Meanwhile, a Chinese businessman comes to the city looking to acquire an antique emerald medallion named "Maragatha Naanayam". This stone was owned by an ancient king named Irumporai and is rumoured to be cursed; anyone who laid their hands on the stone died due to a lorry accident, with the lorry rumoured to be driven by the spirit of King Irumporai. He hires a contractor named John (Mime Gopi), who has connections with local gangs that could do the job. He offers ₹10,00,00,000 for the contract, but no one is willing to do the job as they are afraid of the curse. Only Senguttavan, who is frustrated at the small-time work he is doing under Ramdoss, is interested in the offer as he wants to involve himself in something big and challenging. Elango convinces Senguttuvan to approach a local priest (Kota Srinivasa Rao) who could protect them from the curse. The priest hands Senguttavan and Elango a lemon, at which point the ghosts of the 132 people killed by the curse are revealed to them. The priest tells them that if they are going to pursue the stone, they will need to seek the help of one of the ghosts.

Back home, Senguttuvan and Elango complete the ritual to summon one of the ghosts: Elango's uncle Chidambaram. Unfortunately, before the ghost could appear, the duo is interrupted by the news that Ramdoss has died due to a heart attack. During Ramdoss's burial, the lemon accidentally slips from Senguttavan's pocket and falls on Ramdoss's hand, as a result of which Chidambaram's ghost possesses Ramdoss's body and appears in front of Senguttavan and Elango the following morning, much to their shock. The ghost decides to use three recently dead people and possess them with ghosts of three other people killed by the curse to help Senguttavan and Elango in their mission. The first is an old beggar Selvaraj (Sangili Murugan) who died in his sleep alongside the road. The second is a man (Arunraja Kamaraj) who got decapitated in a freak accident. The third happens to be Chanakya, who hanged herself. Chidambaram successfully brings two of the ghosts to their new bodies, but one of them, a Tamil teacher, has trouble staying in Selvaraj's body and keeps jumping in and out of the corpse.

Senguttuvan, Elango, and the three ghosts, now in their borrowed bodies, pursue the emerald stone. Following an initial lead, they interrogate Pandurangan (M. S. Bhaskar) while posing as the henchmen of a powerful local gang leader "Twinkle" Ramanathan (Anandaraj). This leads them to recover an emerald medallion, which turns out to be a fake. However, their methods draw the attention of Ramanathan. He previously rejected the idea of pursuing the stone but changes his mind. After realizing that they recovered a replica, the group continues to piece clues together. They find the man who made the fake, who is now on his deathbed. Before he dies, the man gives them clues to who ordered the fake medallion - a local doctor named Krishnan (Gajaraj) who happens to be one of the men killed by the curse. They find his son, who is also a doctor, and kidnap him. Before they can get him to tell them where the original medallion is, they are caught by Ramanathan's henchmen and are taken to his torture chamber. They manage to escape the torturers and eventually find the original medallion.

Despite Chidambaram's warning, Senguttuvan and Elango touch the stone and are thereby cursed. They arrange for a meeting with John and the Chinese businessman for the exchange, but on the way, they are pursued by the mysterious driverless lorry. John and the Chinese businessman are run over by the lorry and killed. Senguttuvan manages to elude the lorry initially and recover the suitcase full of money. They then run into the Tamil teacher, who is in Selvaraj's body. He tells them that they must return the stone to the King's grave to lift the curse. On the way to the gravesite, they are pursued by both the mystery lorry and Ramanathan's gang, who are hell bent on taking the stone from them. The group manages to elude both and get to the gravesite. Before they can return the stone, Ramanathan's gang shows up. Senguttavan makes a deal with Ramanathan that after he places the stone in the King's grave, he can take it, to which he agrees. Senguttuvan and Elango place the stone in the grave and are therefore released from the curse. Ramanathan has one of his henchmen recover the stone.

Having completed the job, Senguttuvan and Elango bid goodbye to the four ghosts, who release themselves from the occupied bodies. The ghost occupying Chanakya's body allows an emotional Senguttavan to hear at last the voice of Chanakya and also a declaration of love from her. After Senguttavan and Elango bid a tearful farewell to Chidambaram, all four bodies are laid to rest.

During the credits, while Senguttavan and Elango are boarding a bus to return home, they bump into Ramanathan again, who is now on the run. He tells them as his henchman had touched the stone, he and his gang were pursued by the mysterious lorry and his henchman was killed, while he barely managed to escape. But a few minutes later, a pilgrim (Brahmanandam) who had earlier encountered Ramanathan and his gang while they were in pursuit of Senguttavan, Elango and the three ghosts, returns the stone to him, thus activating the curse on Ramanathan and the pilgrim.