The movie starts in the genie world where the King of all, Karkimuki is sad he has no son for all these years. After praying to Lord Murugan, his wishes come true and he gets a son. He shows all of his love he supressed all these years and loves him unconditionally. One day, his son asks him to take him to the planet where Siddhars live and so Karkimuki takes him there. Accidentally, his son enters a deep burrow to hide from his father where he disturbs a Siddhar's thavam that has been continuing for a thousand years. An angry Siddhar wakes up and curses Karkimuki that he will sent to Earth as a statue and if he is released by someone, that someone has to say a mandaram for Karkimuki to return to the Genie World.

Thirunavukarusu (Thiru) is an ordinary kid but he is a stammerer. Because of this, he gets bullied in school by his classmates. The teacher does not allow him to read out loud when it is his turn due his stammer. The shopkeeper is impatient to listen to what Thiru wants to buy so asks him to write down whatever he wants. His mother does not listen either, but loves him dearly.

One day on a school trip, Thiru is chased by a dog and falls in a ditch where he finds a doll and releases Karkimuki. Karkimuki refers to Thiru as Deivam and scares Thiru. Karkimuki follows Thiru home, only for Thiru to realise only he can see the genie. Eventually, they become friends and Thiru plays a joke on everyone that used to make fun of him. He asks all his wishes to Karkimuni and has fun. The teacher tells everyone there will be speaking contest at school and Thiru wishes to participate but gets scared because of his stammer. He asks Karkimuki to get rid of stammer and Karkimuni agrees. He starts speaking at the contest only to start stammering again.

Thiru gets upset and cries on the stage, wetting his pants. His mum is helpless and comforts him. Thiru does not go to school for the next days and decides to stay at home. Thiru shouts at Karkimuki for tricking him and Karkimuki apologises saying genies have some rules they must never break such as never bringing someone from dead, never to stop time and to never to cure problems related to the mind. Karkimuki says Thiru has a problem related to his mind and not a condition. Thiru tells Karkimuki never to speak to him again. During a robbery, Karkimuki manages to save Thiru's mum so they become friends again. Karkimuki encourages him to ignore everyone and to go to school so he decides to go but promises his mum he will never do anything without telling his mum first.

At school, there is another contest and Thiru manages to win first prize, shocking everyone who undersestimated him. He hides this from his mum as he thinks she will get mad at him. Thiru asks Karkimuki what he wants and Karkimuki tells him everything that happened, bringing tears to Thiru. Thiru assures the genie he will say the mandaram and reunite him with his son. Day after day, he practices the mandaram but struggles. One day, as he is practicing his mum catches him and asks him what it is. He runs away but she hits him and asks him. Watching this, Karkimuki reveals himself to her and she gets scared. Karkimuki decides to go away as the mum is very scared. Later, Thiru shouts at his mum for sending the genie away as he was the only person who patiently listened to him and no one else listened including her.

He runs up to the terrace to find Karkimuki slowly fading away. Thiru cries and gets angry trying to say the mandaram. He finally manages to say the mandaram and it opens a portal for him to go back to the genie world. As he is about to leave, a kite string out of nowhere flies across and slits Remya Nanbeesan throat, killing her. Karkimuki watches as Thiru cries over his dead mum and decides to bring her back to life which causes Karkimuki to die. Thiru and his mum hugs in tears. A final scene shows Thiru speaking on a stage without stammering.