Sundar Ramaswamy is a highly successful NRI businessman based in US, referred to as a corporate monster due to his ruthless business dealings. He arrives in Chennai to cast his vote in the Tamil Nadu Legislative Assembly election. However, he finds that someone else had already voted in his place. Sundar approaches the Tamil Nadu State Election Commission and demands a stay on the election result for his constituency, an annulment of the fraud elector's vote, and the ability to legitimately cast his vote, to which they agree. He raises awareness among the public regarding fraud voting and finds that many people too faced a similar problem to his when trying to vote. M. Masilamani, the previous C.M of Tamil Nadu, is re-elected, his daughter Komalavalli, and fellow politician and brother Malarvannan "Rendu" celebrate.

Sundar visits his family, whilst rekindling with Nila, who is his brother's estranged sister-in-law. Meanwhile, Masilamani receives suitcases full of black money, as he discovers a journalist, Muthukumar, hiding inside the suitcase, to record evidence of his corruption, and Masilamani kills him and buries the case. Sundar's actions bring him into conflict Masilamani and Rendu. Although Masilamani's party wins the elections, the Election Commission annuls the result based on Sundar's plea to recount the votes, and fresh elections are scheduled to take place within the next 15 days. After many assassination attempts on him by Rendu's henchmen, Sundar decides to contest the election against Masilamani as an Independent candidate and resigns from his company to avoid any conflict-of-interest. Initially unpopular among the masses due to his corporate background, Sundar delivers a speech detailing his rise from a humble fisherman background to a businessman and his struggle from poverty to riches, gaining massive support.

Sundar and his supporters gatecrash an event involving the merger of Masilamani's party with the opposition. After Sundar confronts Masilamani regarding his silence on district-related issues, the police brutally beats up Sundar and his supporters. At this juncture, he realises that the entire political system in the state and country needs reform, so he decides to contest in all constituencies in Tamil Nadu along with his supporters. Sundar acquires video evidence wherein people who had attempted to expose Masilamani's corruption were killed under mysterious circumstances, and he plans to reveal it to the media to discredit Masilamani and have him arrested. Meanwhile, Masilamani's daughter Komalavalli, based in Canada, arrives in Chennai after finding out that her father and uncle have lost support due to Sundar. She decides to spoil Sundar's reputation and frame him as a corrupt and power-hungry person.

Komalavalli orchestrates a car accident, planting a case of money, which is stolen by a mysterious person, blaming Sundar for the accident, which causes him to lose considerable public support. She furthers her agenda by killing her father with an overdose of diabetic tablets so that her party will gain sympathy votes. These crimes ensure that Komalavalli, the new Chief Ministerial candidate for her party, would likely win the election. On Election Day, Twitter messages generated from Muthukumar allege that Sundar has stashed black money in various locations, which further degrades Sundar's reputation. However, unknown to anyone, the tweets were sent by Sundar himself, as Muthukumar was one of those activists killed by Masilamani. Further messages lead to Muthukumar's decomposed body being found, exposing Komalavalli's lies.

Meanwhile, Komalavalli finds out that her mother has decided to expose her role in Masilamani's death at the latter's memorial in front of the media later in the day. She arrives at the memorial with her henchmen to stop the expose, but Sundar subdues her henchmen, and her mother's confession is live-streamed, which ensures that the public support is back with Sundar. Sundar and his supporters win the election, while Komalavalli and Rendu are arrested for their various crimes. However, Sundar decides against becoming the Chief Minister, and instead chooses one of his supporters, an honest collector, to be the next Chief Minister.