Pother Kanta starts off like many of the Byomkesh Bakshi novels while Ajit and Byomkesh are having a conversation in the living room of their Harrison Road flat. Byomkesh has noticed a rather unusual advertisement hidden away in the classifieds section of the "Dainik Kalketu" daily with the heading "Pother Kanta" (Thorn of the Road). Translated the ad reads, "If anyone wants to remove the "Thorn of the Road", stand next to and hold on to the lamp-post on the southwest corner of the Whiteway-Ladley store on Saturday evening at 5:30." Byomkesh had noticed this peculiar ad being published without fail every Friday for the previous three months. Byomkesh immediately inferred that the person posting the add went to great pains to remain anonymous and chose this cryptic message on purpose. He also selected a meeting place in the centre of Hogg's Market in Calcutta at a very busy time of the day, so that he could pass by the responder without being detected. Byomkesh guessed that the advertiser would probably want to slip something into the responder's pocket, perhaps some instructions, and would want to accomplish this without being detected. Ajit argued that all of this was circumstantial evidence at best and challenged Byomkesh to prove it, a challenge that Byomkesh heartily accepted.