"You need to whittle down the book you have read into a theme and a idea and a half and then only it becomes a successful film," he said.

Dibakar and his co-writer Urmi Juvekar, who also wrote the screenplay of ‘Shanghai’, finished the script in a year and after that they spent two years researching about the Calcutta of 1943, which was to play a key character in the story.

"A successful detective story is about time and place. You cannot imagine ‘Sherlock Homes’ without Victorian London.

Similarly, you cannot imagine ‘Byomkesh Bakshy’ without the mid 20th century Calcutta. It’s a deeply present in the characters and in the story. One had to bring Calcutta alive.

"You can’t show a little bit of drama and take a documentary short of Calcutta. The story, character and the setting have to be integrated into one mass," he said.

‘PK’ actor Sushant Singh Rajput is playing the titular character in the movie, co-produced by Dibakar and Yash Raj Films. The director said he needed a young face on his way to stardom to play Byomkesh.

"I wanted an actor who is on his way to become a star but is not bigger than his acting persona. I wanted a star who takes acting very seriously. I wanted a young actor who is vulnerable because Byomkesh in my film is on his first case," he said.

The film also marks the debut of Divya Menon, who was the assistant of designer Sabyasachi Mukherjee, and plays the wife of Byomkesh.

"I think I made many enemies in the industry for making this film. I took auditions of many actresses but I couldn’t cast them because I wasn’t creatively satisfied with them.

Satyavati (his wife) is an essential character in the film," he said.

The director has brought the rights of Bandyopadhyay’s other Byomkesh Bakshi stories and hopes to give them big-screen treatment in the future.