Aadhavan - Surya

• Surya Sivakumar as Aadhavan/Madhavan/Murugan
• Nayantara as Tara
• Anand Babu as Tharani
• Vadivelu as Banerjee (Baner Kuppaa)
• Ramesh Khanna as Ilayaman (Kuppusamy)
• Murali as Judge Subramaniam
• B. Saroja Devi as Judge Subramaniam's mother/Madhavan's grandmother
• Sayaji Shinde as Ibrahim Rowther
• Rahul Dev as Abdul Kulkarni
• Sathyan as Murugan
• Anu Haasan as Anu/Thara's Mother
• Riyaz Khan as Police ACP Ravikumar
• Manobala
• Kiri Jeyam
• Alex
• K. S. Ravikumar in a special appearance
• Udhayanidhi Stalin in a special appearance

Story

The film opens up in the city of Chicago, located in the United States of America with a deal of killing an enemy going between the members of two mafia organizations. They identify the man and find out that he will be visiting Kolkata, India in a week and hire an assassin in the name of Ibrahim Rowther (Sayaji Shinde).

The film then shifts to introducing Tharani (Anand Babu), Rowther's son and his foster brother, Aadhavan (Surya Sivakumar). After helping their father finish the transaction successfully, they are contracted by Abdul Kulkarny (Rahul Dev) to assassinate a prominent Judge of the name Subramaniam (Murali), who is presently working on child kidnapping and murder cases in the East Indian belt for sale of their organs to foreign countries. Aadhavan fails to shoot the judge on the first attempt and angry with himself for having missed his shot, he promises to finish his mission. He then proceeds to use the judge's innocent servant Bannerjee (Vadivelu) to get into the family home as Murugan, Bannerjee's brother-in-law. He locks up Bannerjee's real brother-in-law, Murugan (Sathyan), in a ship and threatens Bannerjee with his name all the time. Slowly Aadhavan, as Murugan, begins to win over the members of the judge's household beginning with the judge's mother (B. Saroja Devi), and eventually and finally, his niece, Thara (Nayantara). He attempts to assassinate the judge in the middle of the night and also plants a bomb in the van while the judge is traveling to Darjeeling, but both attempts fail. In Darjeeling, Aadhavan is handed over a guitar belonging to the aspiring wannabe musician, Ilayaman (Ramesh Khanna) by Thara to hide away. He plants a mobile bomb in the guitar and places it in one of the cars which soon explodes.

Thara is now suspicious but Murugan informs her in secret that he is in fact the judge's son Madhavan who ran away from home when he was ten. Thara soon informs all the members of the household except the judge and Ilayaman that Murugan is Madhavan, although in private Muruguan tells Bannerjee that he was only joking and that he is not Madhavan.

However, on Thara's birthday, Aadhavan shows that he is indeed Madhavan. In a flashback, it is shown that a young Madhavan carried a gift for Thara, where a bomb had been planted by Madhavan's friend's mother as an act of revenge. Madhavan's father had put her husband in jail. Though Thara survives, her mother (Anu Hassan) opens the box and gets killed along with her husband. Madhavan runs away from home after stealing a gun from the police, accidentally shooting his father and killing his friend's mother who planted the bomb in the toy. He reaches Kolkata and finds a home in Ibrahim Rowther's place after saving him from his enemies.

Meanwhile, Abdul Kulkarny is fed up with the attempts of Aadhavan and Ibrahim Rowther and decides to play his cards in another way. He persuades Ibrahim and his gang to surrender to the police and make a confession regarding Aadhavan. When Police ACP (Riyaz Khan) confronts Aadhavan and is about to have him hauled off, Aadhavan takes the judge and Thara hostage after shooting the ACP in his leg. He also takes the laptop and memory stick where the entire information about the culprits involved in the child kidnappings and murder case are stored. Later, the police commissioner arrives to reveal a further plot twist: Aadhavan is indeed Madhavan, the judge's runaway son. The police had caught him when he was making his escape after his attempt to kill the judge had failed. It was then that he made his confession of being the judge's son. The police asked him to go back to the house to protect his father over a twenty four hour period everyday.

This information is relayed to the judge who is tearfully grateful to his son. Meanwhile, Abdul Kulkarny attacks the vehicle in which the judge, Madhavan and Thara are traveling and a fight ensues where Kulkarny is ultimately killed in his helicopter. All ends well and Bannerjee says he has brought two new servants for the house, who ultimately turn out to be K.S. Ravikumar and Udhayanidhi Stalin. Madhavan is asked to inspect them. He rates them as awesome jesters, and the judge hires them,ending the film successfully.