Setarer Sur revolves around five friends -Sunil, Brajesh, Ranjan, Suhash and Avijit -who are all attracted to their common friend, Basobi. Basobi seems to be close to Ranjan. Then, she suddenly declares she will marry Brajesh, as she has always been in love with him. Just days before the wedding, Basobi is found dead at home and renowned detective Kiriti is approached to solve the case.