Barath Neelakantan's K-13 opens with an extreme close-up of Mathiyalagan (Arulnithi) strapped to a chair inside a flat. When he tries to wriggle his way out, the chair moves a bit, and the camera slowly zooms out to reveal a dead body behind him. He unshackles himself and tries to check whether the person is actually dead.  As he brings his hand closer to the corpse, a housefly comes out of the dead woman's nose and zooms past his ears. Right from the start, the film earnestly tries to be different and succeeds at it, to an extent.

Within the first few minutes, we start rooting for Mathi and we want him to escape from the house. Usually, a film with such a narrative ends with the protagonist coming out on top, but the way it is told makes all the difference. It has a non-linear screenplay and the happenings are organic. In the process of escaping from the chair, his shirt gets soaked in blood. There are people on the lobby of the apartment, due to which Mathi gets trapped inside the flat on the 20th floor. None of these conflicts are force-fitted, which makes it difficult to guess whether this is a murder or a suicide or an illusion.

K-13 is also purely cinematic to say the least, because there are minimal dialogues, and the visuals tells stories. The portions inside the flat have a lot of closeup shots of the characters. The ones outside the apartment are usually mid shots or extremely wide ones. These close-up shots create a sense of being trapped inside the house along with Mathi, which makes us put our thinking hats on.

In fact, a few portions of the film are set in Sherlock's Pub (for beginners, Sherlock Holmes is a fictional character famous for solving mystery cases). Mathi meets Malarvizhi (Shraddha Srinath) in this pub, who is a writer. Further information regarding Malarvizhi would end up as a spoiler, but all I can say is that she nails the role with her intense acting and nuanced expressions. In a scene where she narrates her story to Mathi, (who is high on alcohol and weed) he doesn't pay much attention. Her eyes convey that she is torn between the feeling of being relieved and frustrated because she vented out her emotions but he wasn't paying attention.

The way Mathi is characterized impresses us more than how Arulnithi portrays it. He is someone who feels nauseous when he sees blood. He is slightly acrophobic, and his legs tremble a lot when he is standing on the sun-shed of the 20th floor of the apartment. In short, he is one among us - a human in flesh and blood. Sam CS's background score is heavy on the bass, and it complements the narrative by creating a sense of impending danger. Although the music,  camera work and acting help in adding the 'mystery' effect, the same can't be said about the screenplay.

A few flashback scenes involving Mathi and Malar takes its own time, and a section of audience might find these portions a bit lagging, but the less than two hours run time compensates for it. The director must also be appreciated for taking mental health seriously and handling depression in a matured way. This is a no-nonsense experimental film, and is very straightforward about what it wants to achieve.