The film opens with Vincent Asokan as Dhivakar, an IT company owner, and his family celebrating his birthday. A sudden, violent lightning strike devastates the moment, killing Dhivakar and his young son, setting a grim tone for a mystery that will unfold with cold precision. In a separate, grim moment at a cinema, a man gropes a woman, drawing a crowd until Aadukalam Naren as ACP Paul Dhanarajan steps in, only to die in the middle of a police conference three days later. This offhand tragedy becomes the catalyst that pulls the other threads of the story into focus.
The detective at the heart of the investigation is Vishal Krishna as Kaniyan Poongundran, known simply as Kani, who shares a cramped life with his associate Prasanna as Manohar, affectionately called Mano. Their world expands when they encounter Mallika, portrayed by Anu Emmanuel, after a pickpocketing incident brings her into their orbit. She later becomes a housekeeper at Kani’s home, weaving herself into the case with an uneasy purpose. A schoolboy named Naveen introduces a troubling new layer: his pet German Spitz Nemo has been shot, and the bullet—nine millimeters—has ricocheted from Nemo’s body. The boy hands over the bullet, and Kani begins to trace its path, a thread that leads him to a tooth found at the crime scene, tied to Swarnavel, a former university physics professor who now lives as a stockbroker.
Meanwhile, a shady figure named Kamalesh visits a travel agency to deliver a sofa stuffed with money to five people who run the operation, a group alleged to be assassins: Devil, Muthu, Pritha, a stout man, and a bald man. The investigation deepens as Kani recollects a news article about the deaths of Dhivakar and his son and confirms Swarnavel’s presence at a nearby construction site on the day of the tragedy. His theory: Swarnavel engineered artificial lightning to kill Dhivakar. When the assassins learn that Kani is tracing them, Devil sends a message by disposing of Swarnavel’s body to cover their tracks, and the web tightens around the investigators.
Kaniyan and Mano press forward to Dhivakar’s office, discovering that a tender Dhivakar was contesting has shifted into the hands of Ram Prasad, the head of the rival company. Before they can reach him, Ram Prasad is assassinated. Kamalesh escalates the stakes by hiring Chinese mercenaries to kill Kani, yet the detective outmaneuvers them. Kamalesh’s plan collapses when Pritha kills him, a twist that reveals how personal loyalties and greed intersect in this deadly game. A police pursuit ensues as Pritha and the bald man attempt an escape, but the bald man ends his own life, enabling Pritha to slip away. In a bustling shopping mall, Mallika comes to Kani’s aid just as Pritha makes a second, failed attempt to strike.
A new alliance forms as Kani and Mano meet Police Inspector Madhivanan and Shaji Chen as Vijayakumar at a hotel, and yet another assassination attempt erupts. Muthu, the other member of the feared crew, plots to inject Kani with a poison dart, but Mano is caught in the crossfire and rushed to hospital. The pair raid the travel agency, where Devil repositioned the dead end by killing Muthu to preserve their secrets. In a crucial turn, they uncover physics books that point toward the science behind the lightning scheme.
A chilling SMS arrives, threatening Kani’s loved ones, and he makes sure Mano’s safety is secured in the hospital, though Mallika is fatally stabbed by Devil before help arrives. Madhivanan is revealed to have been an informer for Devil all along, exposing a larger conspiracy. In a pivotal interrogation, the investigation unravels the backstory: Ram Prasad hired Devil and his team to assassinate Dhivakar to seize the tender, recruiting Swarnavel to design the artificial lightning. Swarnavel’s conscience overwhelms him after seeing Dhivakar’s son—a boy who resembled his own— and he plots to expose the scheme. Devil and his crew intervene, killing Swarnavel and hiding his body in the office refrigerator; Nemo bites Devil when he tries to kill the dog, a small, fatal reminder from the animal kingdom.
Paul’s earlier case—a rape investigation at a hotel—lurks in the background, and Devil’s team eliminates him when he nears the truth, a reminder of how the conspiracy reaches into every corner of the city. With the net closing in, Kani, Mano, and a dedicated police team pursue Devil to a mangrove forest. In a stark, brutal confrontation, all die except Kani, Mano, and Vijayakumar, who survive the assault only to be captured later by Devil, who uses Naveen as leverage to tighten his grip on them.
Bound and outmaneuvered, Kani reveals how he uncovered Devil’s backstory and convinces Devil that the authorities have the truth. Enraged, Devil tries to stab Kani, but Mano frees them and the two manage to overpower him. The final duel ends with Kani delivering the fatal blow to Devil, who, in his last moments, apologizes to Naveen for Nemo’s death. In a quiet, melancholy epilogue, Naveen returns home to find a new Pomeranian puppy waiting on his doorstep with a note bearing Kani’s name, a small, somber reminder of the human cost of vengeance and the unresolved ache that lingers long after the killer falls.
