Plot

Byomkesh Bakshi, a detective, is hired by a rich man to investigate the name of an actress appeared in a movie decades ago, who has eloped ever since. The case became complicated when the rich man is murdered by someone for that.

Sharadindu Bandopadhyay's Bomkesh Bakshi again proves to be a mastermind in this crime thriller wherein although a murder case gets difficult as it could be, the famous detective is able to identify the executioner and the mystery behind the killing.

Famous private detective Byomkesh Bakshi and his assistant Ajit are chatting when a new client, Mr Nishanath Sen, knocks on the door. Nishanath is a middle aged person, an ex-judge and a rich merchant. He needs Byomkesh for a very special reason. He is searching for the details of an old Bengali movie song ('Bhalobasar tumi ki jano') and the actress who sang it, Sunayana, as he thinks that she is hiding somewhere inside his huge nursery, Golap Colony, under a fake identity. Nishanath as a judge hanged at least eight people, but after his retirement, due to lingering moral regrets, he has sheltered a few homeless people, who have either long criminal records or other qualities that make them social outcasts. Byomkesh listens to everything and accepts the case. Sen pays him the advance and requests that he visit his nursery.

Byomkesh meets a Bengali movie expert, Ramen Mullick, and comes to know about the movie producer's son Murari. He learns that, when Murari was making love with Sunayana, he was murdered in his own room. 20,000 rupees and many gold ornaments were also robbed from Murari's room. Suspecting Sunayana's role in the murder of Murari, a court issued an arrest warrant against her, but she disappeared and her whereabouts are unknown. Ramen gives the details about the actress and also about the film and promises to assist Byomkesh whenever he needs him.

The next day, Byomkesh and Ajit visit Sen's bungalow and nursery in the 24 Parganas district to meet the residents whom Sen has sheltered. Byomkesh comes disguised as a Japanese horticulturist named Okakura, while Ajit appears as his Indian assistant. Sen shows them the entire nursery including dairy, poultry and an orchid house. He introduces all the residents and Byomkesh photographs everyone. Within a few days, Sen makes another phone call to Byomkesh requesting him to visit again, but the conversation remains unfinished as Mr Sen is bludgeoned to death with a blunt weapon. Byomkesh and Ajit are visited the next day by a police inspector who wants there help on the murder Sen, not knowing of Byomkesh's pre-existing relations with Sen. Byomkesh and Ajit return to the colony and interrogate everyone concerned with Sen's nursery. After a thorough investigation, Byomkesh realizes that the case will not prove easy to solve, as there are several motives and people behind Sen's death. After a few days, another murder occurred inside the Golap Colony: this time the victim is Panu, a deaf-mute and one of the suspects who witnessed Sen's murder. Panu's killer used the same weapon and method as was used to kill Sen.

Byomkesh again reaches the spot, examines everything and decides to records the interrogations with his voice recorder. He interrogates all the suspects: Bijoy (Mr Sen's nephew), Rasiklal, Muskil Mian, Brajo Das (employees of Sen), Nepal Gupta (a professor) and Dr. Das (a physician and sitarist), and all the women, including Mrs Damayanti (Sen's widow), Mukul (Nepal's daughter) Nazar bibi (Muskil's wife) and Banalakshimi - one among the list of suspects. Byomkesh takes an old photograph of Sunayana and tries to match it with all the women under suspicion, but he is unable to make a match.

Shortly after the latest round of interrogations, Brajo comes to Byomkesh's house and confesses about his lord's personal life. He says that Damayanti Sen was not Sen's legal wife but a live-in partner. Many years ago, Sen sentences Damayanti's husband Lal Singh to death for a criminal case. But Lal is not hanged, but rather imprisoned for 14 years because of the concession given from a high court. Lal later kills a person to steal his car. He takes many parts of the car and throws them through Sen's bungalow window every fortnight to threaten him. Lal often visits Damayanti secretly for money. But Byomkesh's investigation reveals many other possibilities too. He finds a tape of Dr. Das playing his sitar in the doctor's room; this tape was played in the background during the murder of Sen (the tape was heard by Byomkesh through the phone). Byomkesh also finds that Bijoy abandoned Mukul for Banalaxmi. Byomkesh knows that Sen would not have agreed to the relationship of Bijoy with Banalaxmi, so there is a chance that Bijoy murdered Sen in order to marry Banalaxmi and inherit Sen's wealth.

In his room, Byomkesh notices a plastic flower, which triggers a new line of thinking in him. He quickly takes the photo of Sunayana and compares it with the four women's photos and goes for a detailed analysis. He calls everyone and finally reveals Dr. Das as the person behind the murder of Sen and Panu. Dr. Das earlier said that he was playing sitar in his room when the murder was happening. But this statement was dis proven when Byomkesh found the tape that was playing in Dr. Das's room during the murder; the argument that he was in his room playing his sitar was Das's alibi. Byomkesh shows them the stolen jewelry and contract papers of 'Sunayana' which Das was hiding for a long time. Banalakshmi, the employee of this nursery, is revealed as the actress Sunayana and the wife of Dr Das. She declares that she underwent plastic surgery to change her face (which Byomkesh realized while contemplating the plastic flower). Finally Banalakshmi confesses that her husband exploited her beauty to make money and how he murdered Murari, Sen, and Panu to destroy all the evidences of his criminality.