The film is about a psychopath killer who commits a crime and purposely leaves 12 different clues around the dead body, especially for the police to solve the crime.
These 12 clues are basically related to 12 different cities and with the help of these 12 different clues - such as pamphlet of english coaching classes, ATM slip, mobile and the sim-card in it, specks of a 40-year-old lady, a map having initials in Chinese, a visiting card, a picture of godown, a broken watch, a bus-ticket, a black colour suit coat, amongst others, the puzzle is solved by the police.
Who is the killer and who conducts the crime, where most importantly why the person does such type of crime is revealed in the climax.