Nil Nirjane is set in a holiday resort where several people have come to spend their weekend. An interesting urban milieu far away from the humdrums of Kolkata is created when we see an unwed mother with an adolescent daughter, a widower father with an adolescent daughter, and an unwed couple. While relationships among unknown people start developing, the manager of the resort leads a slow life and gets entangled with a tribal girl. Suddenly the Cactus band arrives in the resort to shoot for their music video album and the serenity of the place is disturbed…
The film starts with a music video-like title, where glimpses of the story to follow is showcased. Immediately after that Jaya and his boyfriend Aman enters the resort looking for a room. In the resort we find the single-mother, played by Moonmoon Sen with her daughter, played by real-life daughter Raima Sen. Mou and her father are there to spend the weekend. A friendship develops between Mou and Raima, which gradually emerges as a love entanglement.
Cactus, the rock band from Kolkata arrives for a music video and the place is filled with songs, which emerge in music-video format.
Meanwhile, the Jaya-Aman duo, sensing that relationship is not going to last long go for a suicide pact. People in the resort save them from dying and they leave for the city, with the resort in its original serenity.