Mani Kanchan is a film about a brother-sister duo name Kanchan and Mani. They face hardships after their father remarries. Unable to pay a huge amount of debt, the father fixes his well-educated daughter's marriage to the mentally unstable son of the money lender. The brother-sister duo flees from their house and move to Kolkata to start a new life but the sister gets kidnapped. How they fight everyone forms the crux of the story.