In Kumananthozhu, set in the rain-soaked Theni district, a group of women attempt to cross a fast-flowing river using a rope and tragically drown, setting a grim backdrop for the story that follows.
Two masked men shoot two men in a car, then repeat the pattern with two more victims, and finally silence another target. Deputy Commissioner Shakthi begins a meticulous investigation into the murders and quickly deduces that a Russian-made pistol was used, hinting at a coordinated, well-armed operation.
Meanwhile, Selva moves in with Karukkavel and falls in love with Sara. He works as an assistant manager at IBCI Bank. As the case unfolds, he uncovers that the men who died had connections with Rajavelu, a powerful minister. A crucial lead comes from Nallathambi, Rajavelu’s brother, who reveals that someone killed his men on a train and that criminals stole ₹230 crores intended to be shared with area rowdies. Rajavelu urges Shakthi to recover the money.
The romance between [Selva] and [Sara] intensifies as he confesses his feelings. Shakthi is alerted to another murder at a hotel, where the killer also stole money. [Nallathambi] informs Shakthi that his men plan to move ₹150 crores by train and that protection is needed. A clash on the train leads to the money being looted, and a member of [Nallathambi]’s gang shoots [Selva] in the arm. Shakthi reprimands Nallathambi for meddling, while Nallathambi retorts that ₹400 crores have vanished. The henchman admits firing the shot that hit the thief. Visiting [Selva] in the hospital, Shakthi thanks him, and a realization settles in: everyone in that train compartment appears to be a thief. Meanwhile, [Selva]’s friend travels to the village to warn residents to vacate for the money’s arrival. Sakthi erases [Selva]’s address from hospital records, abducts and interrogates the friend, and orders him to plant a camera in [Selva]’s room. The search for a gun in the suitcase fails, and [Rajavelu] instructs [Nallathambi] to kidnap him and recover the money.
Sakthi’s team interrogates relatives, learning that [Sara]’s father, Isaac, was killed in an accident the previous year. [Selva] wages a careful courtship of [Sara], while also confronting danger and deception. Sakthi reveals to [Sara] that her father was murdered and uses that revelation to press [Selva] toward truth and confession. On the political front, [Rajavelu] pushes his brother to secure the money for the election, mentioning an additional ₹100 crores arriving from quarry owners. [Selva] fights off [Nallathambi]’s men but is ultimately arrested by Sakthi at gunpoint; he remains silent. [Nallathambi]’s men kidnap [Sara], and Sakthi reveals the kidnapping to [Selva]. In a series of flashbacks, it’s shown that [Selva] beat [Nallathambi]’s men and stole the money. [Selva] pleads with Sakthi to hand him over to [Rajavelu] and [Nallathambi], admitting he spent the loot.
Flashbacks reveal the past: the women who died at the start were from [Selva]’s village, including the wife of a close friend. [Selva] and his ally discover that 16 bridges were planned by the Public Works Department but never built, and the funds were siphoned. They take the case to court against minister [Rajavelu]. Isaac, [Sara]’s father, is killed in a lorry accident while a separate fire claims [Selva]’s grandfather and five villagers. When Varadhan visits to offer condolences, Selva asks for a gun; it’s revealed that Selva and his friend killed the men. The villagers meet Varadhan, who says one of his men—aligned with [Rajavelu]—can provide vital information.
In the present, the STF surrounds a building as Sirisu shoots at a figure revealed to be Varadhan’s man. The SPF team and Sakthi retaliate, taking down Nallathambi’s men. [Selva] fights [Nallathambi] and his henchmen, but in the final moments [Nallathambi] wrests [Selva]’s gun and accidentally shoots Sakthi in the shoulder. [Selva] escapes with ₹100 crores, while Sakthi eliminates [Nallathambi]. Later, Shakthi visits Kumananthozhu and witnesses a new bridge rising, a sign of the village’s resilience under the weight of the battle fought. In the end, [Selva] proclaims that arresting him would be impossible because the money is black money, insisting the gun once belonged to [Nallathambi], and leaving a cityscape of questions about justice, loyalty, and power in the wake of a tumultuous struggle.
