In the 10th Century AD the glorious Cholas ruled over the land of Tamil Nadu with Emperor Sundara Chola on the throne. Sundara Chola was bedridden with paralysis and there was confusion all over the Kingdom about who would ascend the throne next. The Emperor had two sons and one daughter. The eldest Aditya Karikalan was anointed the Crown Prince of the Kingdom but his uncle Madhuranthakan (whose father ruled prior to Sundara Chola) also wished to ascend the throne as well.
The story begins when Aditya Karikalan sent his trusted bodyguard and friend Vandiya Devan with two messages for his father, the Emperor and the other for his sister Princess Kundavai. Vandiya Devan learns at Kadambur that all the important noblemen of the court led by the Pazhuvur brothers are hatching a conspiracy to crown Prince Madhuranthakan as the next Emperor.
While on his journey, Vandiya Devan also meets a fat Vaishnavan Azhwarkadiyan Nambi (also known as Thirumalai) who wants to meet with Periya Pazhuvetarayar’s wife who was once his sister. Vandiya Devan uses his name to meet with Nandini and she gives him a signet ring.
Nambi in the meanwhile finds out that a gang of Pandya bodyguards is hatching a murderous plan to kill Prince Aditya Karikalan who had beheaded their King and they were being aided with gold right from the treasury of the Cholas by Nandini.
Vandiya Devan goes to Thanjavur and successfully delivers his messages to the King in private. Chinna Pazhuvetarayar suspects his intentions and tries to imprison him. He escapes from the soldiers and ends up in Nandini’s palace where she tries her best to allure him with her seductive beauty. He escapes from the fort through the underground passage and saves Kandan Maran’s life.
He meets Princess Kundavai with the help of Isana Shiva Battar and learns that she is the same woman whom he had fallen in love with at Kudanthai. She then sends a message to Arul Mozhi Varman, her younger brother who is warring in Elangai to come back as soon as possible and hands it over to Vandiya Devan.
Vandiya Devan goes to Kodi Karai and with the help of Poonguzhali, the boat girl, he goes to Elangai.
In Kanchipuram, Aditya Karikalan’s grandsire advises him to bring his brother Arul Mozhi back from Elangai. His friend Parthibendran agrees to go to Elangai and before he left, Karikalan reveals how much he loved Nandini and how she had betrayed him by trying to save the life of Pandya King and then subsequently marrying the old man Periya Pazhuvetarayar.
Kundavai arrives in Thanjavur and her father confesses to her that he had once loved a deaf and mute woman in Elangai who later committed suicide by jumping from the lighthouse. The emperor believes that he sees her ghost in the night but Kundavai suspects that Nandini is acting like her mother to learn the truth of her birth. She also learns that Nandini could be her own sister!
In Elangai, Vandiya Devan meet with Nambi again and they both set out to meet Prince Arul Mozhi and they successfully give him the messages. They also meet a deaf and mute woman who loves the Prince as her own son and saves his life many times. Vandiya Devan is astonished by her resemblance to Nandini and suspects that she might be her mother.
They also receive news that the Emperor has sent two ships to imprison the Prince on the charge that he tried to grab the throne of Elangai for his own from the boat girl Poonguzhali. The Prince leaves his companions and friends along with Poonguzhali to meet the ships. Vandiya Devan gets caught by a pirate ship and the Arabs imprison him. The Prince finds out that the ships that were to imprison him were destroyed by the Arabs. He sets out in Parthibendran’s ship to rescue Vandiya Devan. In the midst of a fierce storm Vandiya Devan kills the Arab pirates with the help of the Pandya gang who later abandon him alone in it. The Prince rescues him and later Poonguzhali rescues them both.
The Prince contracts shivering fever and is incoherent. Vandiya Devan and Poonguzhali take him along with Senthan Amuthan to Nagapattinam Choodamani Viharam to treat his fever. In the meanwhile, Periya Pazhuvetarayar and Nandini who are at Kodi Karai learn that the Prince is lost in sea. Parthibendran falls for the seductive allure of Nandini and is enamoured by her.
Vandiya Devan travels to Pazhaiarai to give Kundavai the news that the Prince has arrive and is safe though the rest of the Kingdom thinks that he is dead. There are riots in Pazhaiarai when the news spreads. Kundavai meets with Vandiya Devan and then sends him to Kanchi with a message for her brother asking him not to meet with Nandini. Nandini had sent him a message with Kandan Maran asking him to meet at Kadambur and Kundavai feared that it was a trap to kill him.
Vandiya Devan and Nambi set out again to Kanchi. Kundavai meets Prince Arul Mozhi and asks him to wait in the Viharam for some time.