Sujitha, Catherine Tresa known as Suji, is a computer science teacher at Arasan High School who bravely files a missing-person report for her student Ramya with the local police. When the authorities drag their feet, she takes the matter higher, appealing directly to the DGP and drawing attention to a troubling pattern of disappearances that haunt the village. Her accusations also name Malaiarasan, the school’s correspondent and head of the Cooperative society, along with his brother Kottaiyarasan, who runs a shadowy illicit operation. To tackle the case, the DGP enlists a special officer to go undercover as a PT teacher at the same school.
Sudha C as Saravanan arrives at the campus, joining forces with Singaram, played by Vadivelu who often acts with an easygoing bravado. Singaram harbors a one-sided crush on Suji and tries to impress her by bringing alcohol for her grandfather, Agasalingam, a gesture that backfires and adds tension to the already precarious situation. When Suji thwarts Malaiarasan’s henchman Amaldass after he harasses her, a deeper conflict erupts: Malaiarasan confronts Suji and attempts to molest her, only to be faced down by the quick intervention of Mutharasu, Malaiarasan’s nephew and a diligent student. In a fierce confrontation at a bar, Agasalingam challenges Malaiarasan to a fight, but Singaram retreats in fear; Saravanan steps in, defeats Malaiarasan and his men, and saves Agasalingam. Suji comes to recognize the man who fought off her attackers as the hero she’s been seeking.
As the truth unfolds, Suji begins to suspect that Saravanan is the undercover officer the DGP sent to probe Malaiarasan and Kottaiarasan. Saravanan, determined to safeguard the students, secures sponsorship to provide shoes for them and, alongside Nadimuthu, a Maths teacher recruited earlier, probes the school for illegal drug activity. Night after night, Saravanan shadows the operations of Malaiarasan’s brothers and watches as a student, Gokul, is pushed to a dangerous edge. Gokul’s fall is not an accident; it’s part of a cover-up by Kottaiarasan. In a decisive moment, Saravanan disguises himself and assaults the illicit operation’s factory, burning it down and crippling the criminal enterprise. Singaram, meanwhile, is drawn into Pattasamy’s scheme to kidnap Malaiarasan’s nephew Muthu to repay his losses, though Singaram’s efforts falter.
The investigation intensifies when Suji discovers a watch she once gave Ramya in the possession of another student, prompting the two to pursue the truth together. They soon uncover that Ramya was killed by Muthu after he was caught secretly filming nude videos of girls in the school bathroom, Ramya being the daughter of Thaiyamma, the housemaid at Malaiarasan’s residence. Saravanan races to rescue Suji as Muthu drags her toward a brick kiln to silence her inquiries, but he arrives in time to rout Muthu’s guards and force Muthu to call his father, Mudiarasan, who is believed to be dead. The revelation about Nadimuthu’s undercover role rocks Saravanan’s world, casting doubt on his own identity.
Saravanan finally opens up about a long-simmering vendetta against the Arasan brothers. He recounts how his wife, Madhavi, who served as a personal assistant to Minister Maasilamani, discovered her pregnancy and planned to reveal it, only to be murdered in a brutal sequence that condemned Saravanan to prison and torture on false charges. Now free but driven by vengeance, Saravanan teams with Singaram, Nadimuthu, and Pattasamy to loot 100 crores of black money from Mudiarasan. Suji joins them, seeking justice for Ramya and all the victims. The loot is stashed in a locker whose key is split into three pieces; Saravanan holds two, and the trio plots to retrieve the third by kidnapping Charles, a service engineer from Bombay, to unlock the vault. T.M. Karthik is cast as Charles, a crucial piece of the plan, and Singaram pretends to be Charles to repair the locker. A spy camera is planted in Charles’ toolbox to gather intelligence and lay the groundwork for the heist.
As the plot thickens, the Mudiarasan brothers discover Nadimuthu’s true identity as an undercover officer but choose to spare him, believing him harmless. To obtain the final key piece, Saravanan and Singaram infiltrate Mudiarasan’s home, braving obstacles to recover it. The team orchestrates a sophisticated scheme: Nadimuthu sabotages the popcorn machine to draw attention away, Saravanan enters as a service person, Singaram distracts the CCTV operator, and Suji swaps the CCTV footage with recordings from the previous day. A fake threat to the theatre manager Soori collapses, and Saravanan fights the guards while Singaram and Nadimuthu keep Malaiarasan and his men distracted. The vault is breached, and the cash is hoisted out through the ceiling with a bomb-assisted lift.
Just as the heist concludes, Minister Maasilamani and the police swarm the venue, catching Mudiarasan and his brothers off guard. The team escapes the theatre with Saravanan presumed missing, and the others take their share, wondering about his fate. Nadimuthu later learns that the money is hidden inside an air-filled cutout of the actor Vishal in a screening of Madha Gaja Raja, a clue that changes everything. Months pass and the team remains financially strapped, convinced that Saravanan betrayed them. A visit to a prison reveals the truth: the real Saravanan is still behind bars, while the man who led the heist was a fake impostor who had bailed out the original. The imposter receives a tip about 200 crores in black money in Goa, setting up a possible sequel, as Maasilamani and his men brutally torture Mudiarasan and his brothers and leave Madhavi dead in the wake of their ruthless hunt for answers.
