Actor Abhishek Bachchan is currently busy shooting for 'Bob Biwas' in Kolkata. Bob Biswas is an upcoming thriller and a spin-off of Sujoy Ghosh's 2012 hit film 'Kahaani', which starred Vidya Balan in the lead role. Bachchan plays a cold-blooded contract killer in the film and his pictures from the set has gone viral. In the photos, Abhishek is seen in thick, square-framed glasses, wearing a plain shirt with full sleeves and baggy trousers to complement the role of Bob Biswas. Actress Chitrangada Singh, who co-stars with Abhishek in the movie, was also spotted on the sets.