Kaashmora [Karthi] and his family are con artists who cheat people in the name of black magic and dark spirits. One day, Yamini [Sri Divya], a PhD research student, joins Kaashmora to gather evidence and expose him to the public. Kaashmora's growing fame earns him respect from a superstitious and fraudulent minister, Minister Dhanakodi [Sharath Lohitashwa]. When the income tax department raids Dhanakodi's house, his henchmen try to transfer all the illegal money to Kaashmora's house. Seeing this as an opportunity to escape and settle abroad, Kaashmora's family runs with the money.
Meanwhile, Chelapathy Rao seeks Kaashmora's help and brings him to a haunted bungalow on the outskirts of Tamil Nadu and Andhra Pradesh. In the house, actual ghosts haunt Kaashmora. In Chennai, Dhanakodi learns that Kaashmora is a fraud and sends his henchmen to kill his family. The henchmen reach the bungalow but cannot prevail, as the ghosts drag them inside the house.
A broker trapped inside the house, [Tha. Muruganantham], explains that the bungalow was once a princess's palace. Since the princess's death, residents and owners of the house have met with ill fate. He also informs us that there are 13 ghosts in the palace and that Raj Nayak is the head of them all. The trapped people meet Raj Nayak and are commanded to help him reach the spiritual world before the castle locks them in. That night, a young girl in Kaashmora's dream leads him to a closed door within the palace.
As Kaashmora wakes, Yamini tells him that Chelapathy Rao, the man who led him here, died 75 years ago and his spirit took Kaashmora and Yamini here. Kaashmora then searches the castle and discovers an old book dating back 700 years, narrating the tale of Raj Nayak.
Raj Nayak was a self-obsessed warlord and a womaniser. The king tolerated his atrocities because of his military prowess. One day, Princess Rathna Mahadevi [Nayanthara] elopes with the enemy kingdom's prince. The king offers Rathna's hand and half of his kingdom to the man who finds her. Raj Nayak kills the prince and the king, and he marries Rathna while demanding the other half as a dowry. When opposed, he kills the crown prince and the king. Rathna and her friends deceive and seduce Raj Nayak and his subordinates. While Raj Nayak's subordinates are drugged and burned alive, Rathna beheads Raj Nayak when he falters. However, he kills Rathna and her assistants before dying. Before breathing her last, Rathna, wielding witch power, places a curse on thirteen men, preventing them from reaching the spiritual world.
Afterwards, Raj Nayak and the other twelve ghosts haunt the palace and its occupants. An exorcist explains that Raj Nayak would become immortal if five people in a family born under the same Rohini birth star were sacrificed during Navakaali Pournami, a event that occurs once every millennium. Kaashmora recollects that his own family shares the same birth sign and that Yamini is the only woman in her generation.
That night, Navakaali Pournami occurs, and Raj Nayak forces Kaashmora and his family to the guillotine. The young girl from Kaashmora's dream reappears and proves to be Rathna's reincarnation. Rathna's conscience guides Kaashmora to a chamber within the castle where Raj Nayak's remains lie. Using a dagger, Kaashmora destroys the remains, making Raj Nayak vulnerable, while Rathna's spirit destroys Raj Nayak's spirit, sending both to the underworld and breaking the curse. The other spirits flee the castle for the spiritual world. Having escaped the palace, Kaashmora's family returns Dhanakodi's documents and reveals that the spirit guarded the stolen money.
