He initially considered rejecting the script as he was not interested in playing a negative role. Sathyaraj was enjoying good success as a lead actor, when his friend Manivannan narrated the script of Amaidhi Padai to him. Sathyaraj as Ammavasai (later MLA Nagaraja Cholan)/Inspector Thangavel.In his dying moments, Amavasai finally relents and wishes his son happiness in life. But remembering all the atrocities committed by his father, including the deaths of his mother and stepmother, Thangavel guns Amavasai down in a hail of bullets. Amavasai begs Thangavel to spare his life. After fighting Amavasai and his henchmen, Thangavel holds Amavasai at gunpoint. He finds his father's lair where he rescues the girls and stops the tantric rituals. He then takes part in a tantric wedding ritual where his hair is tonsured, and he gets dressed in saffron robes indicating that he has to be a sadhu before his wedding. He forces Kuyili in agreeing to marry him by threatening to kill her younger sister. He kidnaps Kuyili and her younger sister. Thangavel is arrested and jailed.Р В РІР‚СњР В РІР‚С› crooked tantric advises Amavasai to get remarried to a young girl to ensure his re-election. During her funeral, Amavasai acts as a grieving widower which enrages Thangavel who beats Amavasai up in public. Sivakami is murdered by Amavasai's henchman and Thangavel is unable to save her. Amavasai learns of this and plans to kill both. Thangavel informs CBI of the activities of Amavasai while Sivakami plans to testify against Amavasai. He begins to see her as a motherly figure in his life. Thangavel meets Sivakami and realizes she is a good woman. Thangavel is transferred to regular police and gets posted as a Sub-Inspector in the same area. He challenges his father that he will stop all his illegal activities and kill him. Later, he goes to Amavasai's house and reveals his identity. Thangavel saves Amavasai from an assassination attempt. Thangavel is posted as the riot police's head constable where he has to protect Amavasai. A police inspector, who belongs to Dalit caste is burned alive, and the riot intensifies. He instigates caste-based riot in his constituency and pretends to stop it, so that the people will re-elect him. Amavasai realizes that even if the party nominates him, the voters will not support him as they are fed up with his corrupted ways.

Simultaneously, the state assembly is about to be dissolved earlier to hold the general elections. Thangavel now learns of his real father, about the betrayal of his mother and also his father's corruption. He accuses his mother of being characterless to which his grandfather slaps him and tells him about Amavasai. An enraged Thangavel asks his grandparents about his father, but they remain silent. They fall in love, but during their engagement event, a dispute arises as people ask about Thangavel's father's identity, and the wedding is cancelled. Thangavel is betrothed to a girl studying in +2, Kuyili ( Ranjitha). Thayamma's son, Thangavel becomes a Reserve Police constable who is deputed to Amavasai's constituency. He has no children with Sivakami as refuses to let Amavasai touch her, because he had betrayed Thayamma and refused to give Thayamma's son his name even after her death. His ultimate goal is to become Chief Minister where he will have all the power to do whatever he wants, and no one can stop him. To remain in power, he kills anyone who comes in his way. He builds a strong political network through shortcuts. Over the years, Amavasai grows into a highly influential and corrupt politician.

Amavasai marries Sivakami and gets the latter's palace as dowry. Soon, Thayamma gives birth to a boy and dies. Distraught over this betrayal, Thayamma and her parents move out of the village to avoid humiliation. Amavasai finds out that a rich zamindar is looking for a groom for his daughter, Sivakami and he quickly arranges to be married to her as he wants to become rich. His behavior also changes as he grows more arrogant much to the shock of Mani. He changes his name to Nagaraja Cholan to elevate his social status. An enraged Mani instructs Amavasai to stand for the MLA election as an independent candidate to teach his party a lesson. Mani's party refuses to give him the ticket.

One day, he drugs and rapes the barely conscious Thayamma. Meanwhile, Amavasai lusts after a beautiful village belle Thayamma and manages to entrap her with false promises of love. Amavasai helps Mani with some petty tasks during his election campaign. He gets acquainted with politician Manimaran, a MLA of the Palladam constituency, near Tiruppur. Amavasai, is a lazy transient man, but he is also rather shrewd.

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