Cast: Vishal as Detective Kaniyan Poongundran, Prasanna as Manohar (Kaniyan's friend and aide), Vinay as John Richardson Holcha/Devil, K. Bhagyaraj as Muthu, Andrea Jeremiah as Pritha, Anu Emmanuel as Malliga, and Shaji Chen as ACP Vijayakumar.
The film starts with Dhiwakar, a software engineer, his wife, his son, and his daughter, celebrating his birthday on the rooftop of his apartment. A sudden lightning strike kills him and his son. His wife, Mrs. Dhivakar and his daughter watch in horror, as they are burnt to death. At a movie theatre, a man gropes a woman and a small commotion ensues, which was stopped by an ACP Paul Dhanarajan, who later dies in the middle of a police conference.
The movie then shifts to Detective Kaniyan Poongundran, who lives with his friend and colleague, Manohar. He is furious that he does not have a case worthy of his mettle. Later, Kaniyan and Manohar come across Mallika, who is forced into pick-pocketing by her uncle, who is an alcoholic. Kaniyan intimidates her uncle, causing him to reform all of a sudden and offers her a job.
One day a small schoolboy, Naveen, visits Kaniyan and Manohar with a case that his pet dog Nemo, a Pomeranian, was shot dead and asks him to find out the killer. He gives him the bullet collected from the dog's body. With his investigation and the help of a friend, who works in the sciences section of the police department and had asked Kaniyan's help on a previous case, he finds out that it is a 9mm bullet and had been ricocheted from the dog.
At the crime scene, he finds a tooth, with which he collects information about it from a dental hospital and tracks its owner as Swarnavel, who formerly was a physics professor in a university. Kaniyan then understands that there is more to it than meets the eye and starts his complete investigation. What is the relation between the earlier deaths and how the dog's story connects to it and how he puts stop to the murders form the rest of the story.
Thupparivaalan received highly positive reviews and became a commercial hit. Vishal's performance and his chemistry with Prasanna as lauded as the backbone of the film. Mysskin's direction is hailed as slick and the narration as just perfect. The movie is dubbed into Telugu as Detective where it received generally positive reviews.