In the peaceful hill town of Perunad, Ranni, Mohanlal plays Shanmugham, affectionately called Benz, who has settled into a simple life as a taxi driver. His past is marked by fame as a stuntman in Malayalam and Tamil cinema, but he left the film industry after a tragic on-set accident that resulted in the death of his close friend, Vijay Sethupathi who played Anbu. Now, Benz finds solace in his quiet routine, surrounded by his loving wife Lalitha, played by Shobana, their two children, and his prized possession—a classic black Ambassador Mark 1.
Life seems to flow peacefully until one day, Benz’s son, Pavi, a carefree college student, returns home with his friends. Unaware of what’s happening behind the scenes, the boys take Benz’s cherished car, the Ambassador, for a joyride, which ends in a crash. Benz reacts swiftly, slapping Pavi in his anger and disappointment, though he regrets the harshness shortly afterward. Pavi, hurt and upset, stops answering calls from his parents, adding to Benz’s growing concern. In an attempt to repair the vehicle, Benz entrusts the car to his friend Kuttichan, a dependable local mechanic.
Soon after, Benz travels to Chennai to attend the funeral of his former stunt master, a somber event that reminds him of his past. Upon his return, Benz is shocked to discover that his beloved car has been seized by the police. The officials reveal that Maniyanpilla Raju’s character, Kuttichan's assistant, had used the vehicle to smuggle marijuana. Despite the weak evidence against him, the arrogant and corrupt officer, Binu Pappu, refuses to release the car. Benz pleads outside the police station for hours, but it is only when G Suresh Kumar who plays the seasoned CI George Mathan, intervenes that the police agree to release the vehicle—but with a condition.
George, a calm and seemingly composed senior officer approaching retirement, asks Benz to accompany him and the corrupt officer, Benny, to a wedding celebration of CPO Sudheesh’s sister. Though hesitant, Benz agrees, and they travel together the following day. The trip takes a darker turn when George insists on heading to a remote farmhouse in Panchalimedu to continue the celebrations. There, Benz learns a horrifying truth from George—earlier that evening, Sudheesh's sister was allegedly harassed by her ex-boyfriend, who had died in a violent scuffle with her family. In an effort to shield their reputation, George and Benny had hidden the man’s body in Benz’s car, planning to dispose of it in the forest later.
Shaken and overwhelmed, Benz watches helplessly as they dump the body into the forest. The next morning, a disturbed Benz returns home. His wife Lalitha notices blood on his shirt and his distant, haunted demeanor. She reveals that Pavi is still not answering calls, which concerns Benz deeply. When he visits Pavi’s hostel, he learns from the friends that his son left home several days ago. Frustration and anxiety grow, leading Benz to the police station, where officers dismiss his worries by blaming the slap his son received, suggesting Pavi simply went on a trip with friends.
While cleaning his car, Benz makes a shocking discovery—Pavi’s wallet, fallen inside the vehicle. The horrifying realization hits him: the dead man’s wallet belongs to his own son. The devastating truth is that Pavi was the body they buried, and Benz had unknowingly helped conceal his own son’s death. Driven by grief and anger, Benz begins an intense investigation. He kidnaps Sudheesh, forcing him to reveal the truth—that George had orchestrated the entire cover-up, misrepresenting the events and hiding the real story.
Meanwhile, a landslide uncovers the body in Panchalimedu, and forensic analysis confirms that the corpse is indeed Pavi’s. To conceal the truth, George and Benny fabricate a lie, claiming Benz murdered his son over family tensions. It is later revealed that Benz and Lalitha were married, and Pavi was their adopted son, whose biological mother was Anbu—played by Vijay Sethupathi—and Lalitha’s earlier love. This revelation leads to the arrest of Lalitha and her daughter, Mary, who is in love with Pavi, and they are tortured to support the false narrative.
Benz is imprisoned in the police station’s basement, where George plans to eliminate him with the help of corrupt officers. But Benz, fueled by a mix of despair and rage, manages to overpower them, killing Benny in the process and escaping. He calls George, threatening to go after his daughter, Mary. George rushes home only to find Benz waiting with Benny’s body. In a brutal confrontation, Benz uncovers the complete truth: George murdered Pavi because of their forbidden love, and Benny helped cover it up by hiding Pavi’s body in Benz’s car while Benz was unaware.
Enraged, Benz beats George viciously and kills him, as Mary witnesses everything. At Pavi’s funeral, Mary mourns alongside Benz’s family, choosing to stand beside the man she loved despite the tragic circumstances. The film ends with two powerful truths displayed on the screen: > "In India, an estimated 30,000 cases of honor killings occur every year," and > "Yet, shockingly, only 25-35 cases are officially registered. The rest vanish into silence, buried under caste bias and social pressure."
As Benz is led into the courtroom, a reporter asks, "Did you kill your son?" to which Benz responds with quiet resolve, "I didn't kill my son. The ones who killed my son, I..." trailing off as authorities remove the reporters. The story closes with a sense of ambiguous justice and hope, hinting that Mary is now embraced as part of Benz’s family. The final notes reflect on the title “Thudarum,” meaning continuation—symbolizing that life, like stories of truth and justice, moves forward beyond even the deepest pain.
