Manohar moves into a new apartment, 13B, on the 13th floor with his family, fulfilling his life's biggest dream. But they encounter a series of small but strange incidents (such as milk getting spoiled), which are regarded as inauspicious by his family but shrugged off by an excited Manohar. The elevator in the apartment works for everyone in the building except Manohar, which bothers him.
The women in the family get hooked onto a new TV show Yavarum Nalam (Everyone Is Well, or Sab Khairiyat in Hindi). The show is about a family eerily similar to Manohar's who have also just moved into a new house like they have.
As the serial unfolds, Manohar notices that the incidents that happen in the serial are a reflection of what is happening to his family. Things like his sister graduating, his wife getting pregnant and later suffering a miscarriage are all also shown in the serial. Priya is saved by their longtime family friend and doctor, Dr. Balu.
The rest of the family remains oblivious to the similarities and Manohar prefers it that way to avoid panic. He also notices that his camera takes distorted pictures of him while he is in the apartment, but not while he is outside the apartment.
Things start taking a turn for the worse in the serial and Manohar becomes terrified that the same might happen to his family. He now wants to know who is behind the making of the TV show. He then unravels a terrifying secret: the apartment they live in shared their address with a house where a family of eight was butchered back in 1977. It was the family of a TV news anchor named Chitra.
On the day of Chitra's engagement, an ardent fan (Shriram Shinde in the 13B version) of Chitra wanted to stop the engagement and failed in doing so. Disheartened, he committed suicide. Subsequently, all members of Chitra's family were murdered with a hammer in a single day. The blame rested on the lunatic brother in the family, as he had been seen with the hammer last. The police officer investigating the case also committed suicide by hanging himself in the same house.
Manohar and his policeman friend Shiva meet the madman brother Senthil, who apparently goes crazy after seeing the TV show in an asylum. They then meet Chitra's former fiance Ramchandar, who tried to plead for Senthil's innocence because he got covered in blood while he hugged the bodies of his family.
After researching one night, Manohar has a nightmare of the 13B murderer climbing the stairs to kill his family. When Manohar tries to climb the stairs, he always ends up on the 2nd floor. He goes to the hall and witnesses the climax of Yavarum Nalam when they are showing the murderer's identity: Manohar's face is shown as the killer.
What follows is the climax: the 13B murderer is Dr. Balu, who sees the family members' faces as the serial family members. It was he who killed them in the 1970s on behalf of his brother, the spurned fan, and also killed the police officer who caught him red-handed. Manohar kills Dr. Balu.
The story ends with Manohar living a normal life with a new dog in the family; the milk is not getting spoiled anymore. They bring Senthil home and the lift in the apartment finally works for Manohar. Next day,when Manohar uses the lift, he receives a call from Dr Balu, who says that while the 13B family haunts the TV, he haunts Manohar's phone. Finally the lift falls and Manohar plunges to his death.
