This suspenseful investigative thriller follows the trials and triumphs in the life of Chandrasekhar (Mohanlal), an IPS officer who lives a detached and lonely life after being divorced from his wife, Deepthi (Priyamani), a leading criminal lawyer. He lost his sparkle as a police officer after his family breakdown. He lives in a dark and violent city but even when unlawful incidents take place around him, he withdraws himself from all responsibilities and is happy to live quietly.
However, things change when he is made the head of the Metro Crime Stopper Cell in Kochi. In the initial days Chandrasekhar is his cool self, focusing more on household chores and the chessboard on his table. Things seem to change when he single-handedly saves three college girls abducted by a psychologically deviant guy.
Chandrasekhar gets a congratulatory note from an anonymous man calling himself "Z" who challenges Chandrasekhar to figure out how he is going to bump off one target after the other. Chandrasekhar is forced to take up the investigation of the murders, which follows a mysterious alphabetical pattern. How Chandrasekhar unravel the identity of the killer forms the latter part of the story.