Famous Bengali private investigator Pradosh C. Mitter (Feluda) is hired by wealthy businessman Dinnanath Lahiri. His suitcase has been accidentally exchanged with someone on the Kalka Mail. Inside it is a valuable manuscript written by Shambucharan Bose. The case takes Feluda, Topshe and Jatayu to Shimla, where they discover a priceless diamond in a film container, disguised as a betel - nut. 'The Three Musketeers' face great danger in Shimla, before Feluda eventually solves the case.
| Editing | Subrata Roy | Editor |
| Directing | Sandip Ray | Director |
| Writing | Satyajit Ray | Writer |
| Sound | Satyajit Ray | Original Music Composer |
| Camera | Barun Raha | Director of Photography |
| Art | Ashoke Bose | Art Direction |
| Writing | Sandip Ray | Screenplay |