Plot

Two theater artists compete in a small drama troupe.

The two best disciples of Sivadas Swamigal, the earnest owner of a Drama school, are by design pitted against each other by the guru himself and this create multiple calamities ending in the duo's separation. Years pass by as one finds a good holding and the other wobbles away as a drunk loser only for them to cross paths again when the ongoing Indian Independence Movement gives another chance for the tables to turn!—PipingHotViews

Kaliappa Bhagavathar (Siddharth) and Gomathi Nayagam Pillai (Prithviraj) grow up together under the guidance of their guru, Sivadas Swamigal (Nassar). While Gomathi is hardworking and dedicated, fun-loving Kali is the natural performer. His effortless talent and innovative style wins him appreciation of his guru. This is unbearable to Gomathi, who believes he deserves all the laurels. Meanwhile, Vadivambal (Vedhika) joins their troupe. For Gomathi, it is love at first sight, but Vadivambal falls hard for Kali. Kali, however, is in love with Rangamma (Anaika Soti), the daughter of a local king. When Gomathi learns of this affair, he finds a way to deceive Kali.—Saraswathi

Kaaviya Thalaivan is a Tamil Historical period movie. Based on the early 20th century, Siddharth and Prithviraj play the two theatre artistes and Nasser is the guru to these actors and heads the drama troupe. Vedhicka does the role of a stage artist. This movie is about the competition that exists between Siddharth and Prithviraj in their small drama troupe.

Thavathiru Sivadas Swamigal runs a drama troupe in which Thalaivankottai Kaliappa " Kali " Bhagavathar and Melachivilberi Gomathi Nayagam " Gomathi " Pillai are his direct disciples. Gomathi is left by his father in Swami's troupe. Kali is found by Swami during a train trip where the boy is singing and begging for alms. Impressed by his singing talents, Swami takes the boy with him. Gomathi and Kaliappa have a relationship like brothers. They grow up together and stage many plays where Gomathi often plays the "sthripart" (female role), and Kali plays the "sidepart" (supporting characters). Vadivambal joins as the female member of the group and soon falls in love with Kali. Meanwhile, Gomathi falls for Vadivu; however, Kali loves Rangamma, the princess of the zameen. S. V. Bhairava Sundaram, who is another student of Swami, is a popular "Rajapart" (performing main title characters of a stage play). He becomes headstrong over his acting capabilities and does not attend the rehearsals, for which he gets scoldings from Swami. After a quarrel, he leaves the troupe as he could not bear Swami's torture. Swami does not give up and conducts an audition for the main character role of Soorapadman, in which Kali and Gomathi perform. Kali gets selected, which leaves Gomathi angry. The reason behind Swami's bias towards Kali is never answered clearly by Gomathi, which leaves him more frustrated.

After following Kali secretly, Gomathi informs Swami about Kali's love to take revenge on him. Swami scolds Kali and curses him that he will never play any characters on stage, but Kali wants Swami to pardon him and keep him with the troupe as a servant. Swami agrees and asks him to forget the princess if he wants to continue in the troupe. Kali promises, but Swami agrees to keep him with the troupe like a servant but does not take back the curse. The following day, the entire troupe leaves the village and heads to another place. Kali cannot forget Rangamma, and she is also shown to be searching for Kali, and one night, a man from the village comes to Kali to inform him that Rangamma has committed suicide due to the forcing of her parents to get married. The man also says that she was pregnant when she died. Kali, fully drunk, comes to the troupe and curses Swami that he is the reason for Rangamma's and his unborn child's death. Swami gets ill suddenly and dies, but before dying, he blesses Kali, who pardons to forgive him, which drives Gomathi into more anger and jealousy. After Swami's death, Gomathi takes charge of the troupe and wants Kali to be out of it. Kali fights with Gomathi and leaves.

It is shown that the troupe travels to Ceylon, Malaysia, and Singapore in five years' time and becomes popular. Now, Gomathi is a famous "Rajapart" as he wished to be, and Vadivu is known to be the famous "Ganakokilam" Vadivambal. They return to Madurai and join hands with a famous stage play producer named Contract Kannaiah, who produces the plays. When they are getting ready to stage the play "Karnamotcham", Gomathi falls severely ill. He asks the people from his troupe to go in search of other drama actors to perform his role. A man goes and brings Kali, who is a drunkard now. Feeling delighted to see his troupe members, he agrees to play the role of "Karnan", though he is given the role of "Arjuna" by Gomathi, who says that it has been long since they performed together. Gomathi performed well, but was surpassed by Kali as he sings a song and drives the attention of the audience to himself, Gomathi still feels ill and could not perform in any plays. Meanwhile, Kali fills the gap and earns a good reputation as "Rajapart", which makes Gomathi even more jealous. He knows an interest of Kali towards freedom movement stage plays and arranges for a person to get Kali arrested for performing in plays, which is against the British. Gomathi visits him in jail on the pretext of taking him on bail.

Inside the jail, Kali meets other people involved in the freedom movement and encouraged by them, he agrees to do stage plays on that topic. Meanwhile, Gomathi falls in love with Vadivu and pesters her to marry him. Meanwhile, her mother makes arrangements to make her the mistress of a Jamin king. Distressed Vadivu leaves the troupe and waits for a call from Kali to join his "Bharatha Gana Sabha", in which he stages plays based on the freedom movement, due to which he frequently goes to jail. Meanwhile, the audience becomes interested in Kali's plays rather than Gomathi's epic plays. Vadivu gets a call after so much persuasion for which she was waiting and joins there eagerly. She expresses her love, and it is lately accepted by Kali. Gomathi's life changes, and he turns from a rich man to a poor man. Kali is informed about Gomathi's situation. Therefore, he approaches Gomathi and asks him to join his troupe and offers him the "Rajapart" role with fondness, to which Gomathi agrees. They get ready to stage a play on Bhagat Singh, for which the British announce a shooting warrant. However, a brave Kali performs on stage, but when the play ends, the police come and chaos starts. The troupe people ask Gomathi, Kali, and Vadivu to escape. Police follow them, Kali goes alone, and Vadivu and Gomathi escape together inside a forest. A gun sound is heard, and Gomathi leaves back Vadivu to go and see what it was. He meets Kali, who is safe. Kali tells a plan to meet tomorrow morning. While he leaves, he is shot by none other than Gomathi.

Kali is shocked and asks why he did this to his brother. Gomathi vents out his anger for the first time to Kali saying that Kali snatched the "Rajapart" role of Soorapadman, his love interest Vadivu, regained his "Rajapart" status when he fell ill and states that he is now poor because of the increased popularity of Kali's plays. Kali says that he knows it was Gomathi who told Swami about his frequent visits to Rangamma's place, and he also says that he knows the person who made him sent to jail was Gomathi's arrangement, but he took all these as good deeds that his elder brother did for him for positive changes in his life and forgave Gomathi each and every time. Gomathi now feels guilty, but Kali asks Gomathi to shoot him to death and fights with Gomathi. During the quarrel, the trigger is accidentally pressed, and Kali dies. In the last rites ceremony, when everyone is mourning, Vadivu informs that she is pregnant with Kali's child and says that he will be reborn again. Gomathi takes the ashes to Varanasi, and while dipping in the Ganges, it is shown that he never comes out of the water.

The film ends without showing if Gomathi drowns himself to join Kali in heaven.