In the South Indian kingdom of Cholapuram Paalayam in the year 1771, Raja Mokkaiyappar and his queen, Rani Bhavani Ammaiyar are in desperate for a child, as all their previous twenty-two children have died at birth. Unknown to them, Bhavani's brother, Sangilimayan, who is also the Rajaguru (High priest), is responsible for the death of their children. Sangilimayan is shocked to see that his sister has given birth to twins. Before informing the king about the birth, he calls the palace astrologer, Chinnavadayaan, who predicts that the elder twin will be incapable of making decisions on his own while the younger one will be smarter. Sangilimayan orders the palace doctor, Kailasakaruppan, to kill the younger one, but Chinnavadayaan tells Sangilimayan that his actions would not be good for the kingdom. Instead, Sangilimayan orders the palace doctor to abandon the child in a nearby river. The elder child is named Pulikesi XXIII. Maragathavalli, Kailasakaruppan's childless wife, rescues the abandoned child from the river, and the couple decides to raise him as their own, naming him Ukraputhan.

Twenty-five years pass, and Pulikesi is now the king of Cholapuram Paalayam. As foretold, he is foolish as well as lecherous. He is a puppet in the hands of Sangilimayan, who collaborates with the British for his own personal gain, and does not attend to the needs of the people of his kingdom. Pulikesi also tortures his subjects. He creates an outdoor stadium for different castes to fight against each other and punishes his palace guards even when they make the slightest of mistakes; he also uses his guards as targets for shooting practice. Ukraputhan, now an educated revolutionary, collaborates with his friends to overthrow the British. Ukraputhan falls in love with Vasantha Sundari, who reciprocates his feelings. When Ukraputhan plots to overthrow Pulikesi for serving the British, he is shocked to see that they look alike.

Ukraputhan then learns about his birth from his foster-parents and realizes that Pulikesi is his identical-twin brother. To save the land from Sangilimayan and the British, Ukraputhan switches places with an unconscious Pulikesi as the king whilst sending Pulikesi to prison. As the king, Ukraputhan reveals his true identity to Agandamuthu, the commander-in-chief, and joins forces with him to help bring about new reforms. He converts the palace harem into a playground and helps fund and provide for the education of children; to grow crops, he creates fertile land for tilling the soil. In a break with past policies of the kingdom, Ukraputhan refuses to pay tributes and taxes demanded by the British. Bhavani Ammaiyar praises Ukraputhan's reforms, unaware that Ukraputhan is disguised as Pulikesi. In jail, Pulikesi is taken care of by Soolayini, who provides refreshments to the soldiers. Eventually, the two fall in love.

All of this happens while Sangilimayan is away on a business trip visiting British officers in Chennai pattinam. When he learns of the new reforms, he confronts Ukraputhan, who defies him. Later, Pulikesi escapes from prison and overhears a conversation between Ukraputhan, Agandamuthu, and Chinnavadayaan. Pulikesi learns the truth about his birth and realizes his mistake. He reunites with Ukraputhan to reform the kingdom, but is beaten by one of Sangilimayan's men and is locked up in the palace. However, he escapes with the help of Kollan, the palace blacksmith. Believing that Agandamuthu was responsible for Pulikesi's change of mind, Sangilimayan arrests him and Ukraputhan. After escaping, Pulikesi appears before Sangilimayan as Ukraputhan but is recognized by his minister, Mangunipandiyan when he inadvertently uses his catchphrase. A fight between the twins and Sangilimayan follows; Sangilimayan is overpowered by Ukraputhan and is about to be killed when Bhavani Ammaiyar intervenes. Feeling guilty for betraying his kingdom, Sangilimayan, at the behest of his sister, has a change of heart and apologizes to her; she forgives him. The kingdom attains independence from British rule and Pulikesi and Ukraputhan marry their respective lovers, Soolayini and Vasantha Sundari. Pulikesi then introduces 10 ordinances for the welfare of the people of Cholapuram Paalayam.