Maariyappan [Dhanush] is a fun-loving gangster whose loyal sidekicks are Sanikkizhamai [Robo Shankar] and Robert [Kalloori Vinoth], and whose closest ally is Kalai [Krishna Kulasekaran]. His carefree swagger and rough humor define his days, even as he carries out small-time schemes with a crew that keeps him in motion. In the background, Araathu Aanandi [Sai Pallavi]—an auto rickshaw driver—is hopelessly in love with Maari, constantly pursuing him and hoping for his attention, though Maari often responds with irritation and indifference.
The balance shifts when Gangadhar Beeja alias "Thanatos" [Tovino Thomas] escapes from prison after killing two officers. Beeja harbors a deep grudge against Maari, spurred by a promise from his brother, a defence lawyer, to secure Beeja’s release. That brother is killed by Maari when he attempts to molest Aanandi’s elder sister, a fact Beeja does not initially know, and this act fuels Aanandi’s affection for Maari. On a night out, Maari is attacked and Aanandi steps in to nurse him back to health, cementing the complicated bond between them. Kalai’s brother Vallavan aligns with Singayya, who has allied with Beeja to topple Maari.
Beeja’s plan unfolds as Vallavan is directed to send Aanandi away for a job that turns out to be drug smuggling. She unknowingly participates, and Kalai catches her in the act. When confronted, she reveals that Maari had asked her to do it, sowing seeds of doubt in Kalai. A subsequent confrontation leads Maari to seize Vallavan’s drugs, a fight erupts, Singayya is killed by Maari, and his own followers burn the drugs. Beeja then kills Vallavan, cunningly making it look like Maari was responsible. Kalai, enraged and loyal to his own family’s safety, orders his men to kill Maari, who is wounded in the ensuing clash. Beeja reveals himself as the mastermind, shooting at Maari; Aanandi heroically saves him by taking the bullet intended for his life, leaving her paralysed for life.
Into this maelstrom arrives Vijaya Chamundeshwari [Varalaxmi Sarathkumar], the newly appointed District Collector, charged with restoring order and ending gang violence. Maari and Aanandi go into hiding, seeking safety away from the escalating crime and political intrigue. Eight years pass, and Beeja and Kalai have grown into powerful forces. Kalai’s chance to become a legislative candidate poses a threat to Beeja, who uses his influence to pressure Kalai and his family. Vijaya, now the Deputy Home Secretary, helps press Maari’s image into the public eye, posting his and Aanandi’s photos to track him down, while Maari confronts Vijaya and reveals the truth behind the long years of fear and violence.
Maari and Aanandi marry and settle in Tenkasi, living with an older couple who help them raise their family. Aanandi becomes pregnant, but the pregnancy is complicated by her paralysis; she dies minutes after giving birth to a healthy baby boy, Kaali. Maari raises the child with the aid of Sani and Robert, hoping to give Kaali a better life. Kaali inherits Maari’s temperament and starts showing the same fiery streak in school, which prompts Maari to intervene when his son faces bullying and retaliation. He pleads for forgiveness from the local councillor whose son is attacked, but Maari must fight the entire system to protect his family.
Meanwhile, the police department elevates its drama with whispers of an informant inside Beeja’s gang. Beeja exploits the ruse to test corrupt officers, but the plan backfires when it becomes clear there is no mole—Beeja himself has been leaking information to clear his own name and to position himself for political power. The tension escalates as Beeja tries to manipulate the department, only to be confronted by Maari’s relentless pursuit of justice and family protection.
In a final confrontation, the police turn against Beeja. Maari engages Beeja in a brutal showdown and paralyzes him in revenge for Aanandi’s sacrifice, also revealing to Beeja that Maari killed his brother to stop him from harming Maari for wealth. Beeja is sentenced to life in prison, and Maari remains as the steadfast patriarch of his household, continuing his old life with Kalai by his side. The movie closes on Maari’s quiet resilience and his return to the world he knows, where loyalty, love, and a hard-won sense of justice guide his every move.
