Via Darjeeling is about a couple Ankur (Kay Kay Menon) and Rimli (Sonali Kulkarni), who are recently married and are on their honeymoon in Darjeeling. However, just before they are to return to Kolkata, Ankur disappears. Robin Bose, the inspector in charge of the case, starts a search for Ankur but cannot find him. Rimli tells him about a taxi driver whom Ankur had fought with and a suspicious looking man whom she thought had followed her throughout their trip in Darjeeling.
After two years, in an 'adda' 'session, on a rainy night, Inspector Bose relates this story to a few friends. They are captivated by the story and start specultaing about the outcome. Each of the friends take turns in narrating their own hypotheses in unraveling the mystery and in an interesting turn the past and the future mesh and blend into the story itself.
The movie is set in modern day Kolkata and Darjeeling and exults in the tradition of the Bengali 'adda'