It was a chance encounter with the first investigative officer in the 2008 double murder of Aarushi and Hemraj in Noida that propelled Vishal Bhardwaj to write 'Talvar'.
Taking inspiration from Akira Kurosawa's "Rashomon", Bhardwaj set out to examine the nature of the truth in the case, where Aarushi's parents Rajesh and Nupur Talwar were convicted.
"Some of the things that I found were really amusing, bizarre and disturbing. There was a kind of black humour that was coming out of this tragedy. I am a great fan of Rashomon.
I found the best way to write the script in it," he said after the film's Indian premiere here last night.
"Of course, my feelings would come in the way but we wanted to be fair to everyone. We have added nothing from our side... It was a painful journey and it scares me to think 'What if I or anyone gets sucked into the system which we have? What will happen then?'"
Another thing that troubles Bhardwaj is that while everyone talks about the death of Aarushi, people don't really think much about Hemraj.
14-year-old daughter Aarushi was found dead in her room of her flat in Noida in 2008. Aarushi's parents - Rajesh and Nupur Talwar are in Dasna jail in Uttar Pradesh after being convicted for their daughter's murder.
Director Meghna Gulzar said the most difficult part for her was to film the actual murders.
"There was nothing more difficult than filming the actual murders. There were different weapons and different perpetrators but the one to die was always the girl and the man. That did not change and it was not easy. The film needed to be neutral so I needed to be objective but you are human and you do react to the information that is facing you."
Irrfan, who plays a character based on CBI officer Arun Kumar, said he met him to prepare for his role.
"A murder mystery on a real incident sometimes becomes a source of sensationalism but this story was so near and so frightening that I got sucked into it.
"It is an important case and whatever you may think about the verdict, the film gives us a chance to look at our system and how different departments deal with a crisis."
Konkona plays a role that is based on Nupur Talwar and the actress said her part was well researched.
"It is not a character study, so I did not get into that. What I found interesting as a performer was portraying guilt and innocence according to perceptions. There is a thin line between guilt and innocence and I liked that ambiguity. It is a very well-researched film."
Produced by Bhardwaj and Junglee Pictures, the film will release on October 2. The release comes after a well-received world premiere of the film at the Toronto International Film Festival.