Byomkesh O Durgo Rohosyo is a Bengali detective thriller starring Dev as Byomkesh Bakshi, Ambarish Bhattacharya as Ajit, and Rukmini Maitra as Satyabati. The film is based on the famous detective story by Saradindu Bandyopadhyay.
The story begins when Professor Ishan Chandra Majumder dies mysteriously at the ancestral fort of the wealthy Singha family. Byomkesh Bakshi and his close friend Ajit are called in to investigate the case.

According to the initial police investigation, the professor died from a snakebite. However, as Byomkesh begins examining the circumstances surrounding his death, he discovers that the fort is hiding several dark secrets. The family has already experienced a series of unusual deaths, including the mysterious deaths of family members under suspicious circumstances.

As Byomkesh investigates further, he learns about an old legend concerning a hidden treasure buried within the fort. The mystery becomes more complicated as family rivalries, secret motives, and suspicious behaviour raise questions about who can be trusted.

With the help of Ajit and DSP Purandar Pandey, Byomkesh carefully examines the clues, connects the deaths, and searches for the truth behind the family’s secrets and the legendary treasure.