An insider reveals that Dibakar Banerjee had approached Aamir to play villain's role in his film. When Aamir had got the narration from Aditya Chopra for Dhoom 3, at the same time Dibakar had also narrated Detective Byomkesh Bakshy's script to him.
The common thing was that both the roles offered to Aamir were negative and he had loved both them. Also, Aditya Chopra is the producer for both films. It was a path breaking step for Aamir to portray a negative character. This had put him in a big dilemma but he had already chose to go by Dhoom 3.
When asked Dibakar, he said "Byomkesh Bakshy was the story I wanted to make after Khosla. The studio I was in talks with loved the project and we thought the best guy then to do the baddie was Aamir. We went and narrated to him. I didn't know that Dhoom 3 was on the slate next with Aamir as the villain. Aamir passed on my script. Two years later we met after the Byomkesh teaser had released - and he had just loved it. I guess Yrf's gain was Yrf's loss!"
Apparently, the villain of Detective Byomkesh Bakshy! has a very strong role in the film. Dibakar is not revealing the villain's identity anytime soon and plans to keep it under wraps.