On the night of a party, Vasantha, Kanchana discovers her husband Ranganatham dead and narrowly escapes an attempt on her life by a masked murderer. In shock, Vasantha becomes mentally paralysed. A police investigation, led by a police inspector, follows the incident and sets a tense stage for what’s to come.
Meanwhile, Susila (Susi), a college student from Madras, arrives at the house for her holidays, along with her friends. She lives with her three younger paternal uncles: Ranganatham (the victim in the opening scene), Rajasekhar, and Chandrasekhar. Also residing in the house are her aunt Vasantha, who was almost the murderer's next victim, and the butler Naganna. The house is frequently visited by Ramayya, Rajanala Kaleswara Rao, an old Ayurvedic doctor and close family friend. Susi's parents had passed away long ago, leaving her under the care of her uncles and aunt.
During her stay, a chilling series of murders unfolds within the house, with the killer consistently leaving a cigar bit at each crime scene. Vasantha, the only eyewitness to the murderer, is placed under tight security but is eventually killed, plunging the household into deeper fear. The murderer repeatedly calls Susi, threatening that she will be his next target. Susi feels increasingly unsettled by the events and the menacing phone calls that keep her on edge.
Afterwards, Susi meets Bhaskar, a young man who eventually falls in love with her and promises to help. Bhaskar, Krishna, investigates Chandrasekhar and later Rajasekhar, following Rajasekhar to a strange house where a woman wanders like a ghost. She is revealed to be Rajasekhar's lover, whom he had rescued years ago after she attempted suicide. Rajasekhar had kept their relationship secret, as he wanted Susi to marry first before he could marry his lover.
To lure the murderer, Bhaskar sends everyone away for the night. As expected, the murderer attempts to kill Susi, but Bhaskar fails to unmask him, only seeing his eyes before the killer escapes, leaving his mask behind. Then, the doorbell rings and Bhaskar answers, only to find Chandrasekhar murdered at the doorstep.
Rajasekhar urges everyone to vacate the house after celebrating Susi's birthday party. During the party, the murderer shoots at Susi but misses. Bhaskar chases him but loses track. He later finds Ramayya injured in the garden, who tells him that the masked man attacked him and ran away. The family begins to theorize the motive behind the murders and discuss the killer's identity. Ramayya urges Rajasekhar to reveal his family’s past, which leads to the revelation that Rajasekhar’s father had an extramarital affair with a woman who bore him a son. When Rajasekhar's father was on his deathbed, the woman and her son were allegedly forced out, and they died 15 years ago in a fire set by Susi's father.
Bhaskar deduces that the son may have survived the fire and is now seeking vengeance as the murderer. Since the killings are taking place 15 years after the fire, and the murderer appears to be about 25 years old, Bhaskar’s theory is confirmed. He believes the killer is present in the room with them, as he has seen the murderer's eyes multiple times. Bhaskar has everyone line up and places the murderer’s mask on each man’s face to compare the eyes. He eventually exposes Ramayya, Rajanala Kaleswara Rao, as the murderer, who had used prosthetics to disguise himself.
Ramayya confirms Bhaskar’s theory, revealing that he survived the fire and witnessed his mother dying in the flames. He swore vengeance on the family and has been killing them ever since. When Ramayya attempts to kill Rajasekhar and Susi, Bhaskar intervenes, and a fight ensues. The murderer escapes, but Bhaskar chases him. In the ensuing struggle, the police shoot Ramayya, and he disappears into a tunnel in the garden. The family discovers a secret room beneath the garden that leads to the murderer’s hideout, realizing it was the secret escape route used after each murder. A tearful Rajasekhar sees the murderer's dead body and acknowledges him as his brother, and the film ends with Bhaskar marrying Susi and staying happily in the house, while Rajasekhar marries his lover.
