Well-known Bengali non-public investigator Pradosh C. Mitter (Feluda) is employed by rich businessman Dinnanath Lahiri. His suitcase has been by accident exchanged with somebody on the Kalka Mail. Inside it's a useful manuscript written by Shambucharan Bose. The case takes Feluda, Topshe and Jatayu to Shimla, the place they uncover a priceless diamond in a movie container, disguised as a betel - nut. 'The Three Musketeers' face nice hazard in Shimla, earlier than Feluda finally solves the case.
