[7] Ranjith Kalidoss is a DSP in CB-CID, who along with Inspectors Joseph and Vandana, takes on high-profile cases and closes them successfully.

Ranjith's superiors assigns his team a task to pursue a group of 5 criminals, who continue to avoid justice with their political and economic influence.

A parcel arrives at the police station one day that contains a small horse doll hanging on a noose.

A few days later, Shivanand, a local communist leader, goes missing and is later found in the warehouse hanging from the ceiling, tortured and his face covered in an animal mask, very much like the doll they received.

The killer continues to taunt the team by sending clues as he kills more people, which includes Vishnu, a lawyer and Dr. Ramya, a pathologist.

When his team arrives, they inform him about a dead body in one of the buildings, but he already knows and describes what he would find without seeing it, also deduces that he himself is the killer's next target.

Back at the office, Ranjith manages to piece things together and connects the serial killings to a case that he investigated a few years earlier.

Emmanuel and his wife are a rich architect couple in town, who lived with their 16-year-old daughter Catherine and a caretaker Mariadas.

Not able to wiggle their way out (as Ranjith and Vishnu refuse to take bribes and hush up the truth) and driven by guilt, Emmanuel and his wife hang themselves.

Dr. Ramya is involved in the autopsy of Catherine, and the prosecutor is set to argue the case at the court and is present with Ranjith during the interrogation and confession.

A cop is dispatched to Christopher's house to investigate, and he finds all the evidence supporting their theory, but before he could alert his team, he is killed.

A few days later, Joseph and Vandana meet Ranjith at his house and ask him why he did not inform the press that Christopher was the serial killer.

Likewise, Varalaxmi Sarathkumar was selected to appear as a police officer, and Sruthi Hariharan was signed on to play the wife of Arjun's character.

For Nibunan, a critic from The Times of India wrote, "watch it for the suspense-filled plot which has decent family moments, the surprise killer and the way the team uncovers the mystery through mind games", while rating the film with three and a half stars.

[22][23] Likewise, The New Indian Express's critic wrote it was a "smart thriller" that "manages to extract thrills and nuggets of applause from a display of the vagaries of human psyche".