BOB BISWAS is the story of a contract killer who has lost his memory. Bob Biswas (Abhishek A Bachchan) is married to Mary Biswas (Chitrangda Singh) and has a son Benny (Ronith Arora) and daughter Mini (Samara Tijori).
8 years ago, Bob met with an accident and has been in a coma since. Bob regains consciousness but has no memory of his past life. He doesn't even recognize Mary or his children. Bob tries his best to adjust thanks to Mary who provides him with all the love and support to sail through this difficult time. Slowly, Bob forms a bond with Benny and Mini. He learns that Mini is his stepdaughter and that Mary was earlier married to David (Karanuday Jenjani). Bob married her after David passed away in an accident.
One day, two police officers, Jishu Narang (Bhanu Uday Goswami) and Kharaj Sahu (Vishwanath Chatterjee), take Bob Biswas to a hideout. They inform Bob that he is a contract killer and that he has worked for them in the past. They start giving him contracts to kill people. Bob, at first, is apprehensive but he soon goes for it. His first two victims are Bubai (Purab Kohli) and Rahul (Kunal Verma), both of whom were in the business of selling a powerful and banned drug, code named 'Blue'. When Bob goes to kill Rahul, he suddenly gets flashes of his earlier life. He also realizes that David didn't die by accident but was killed. What happens next forms the rest of the film.