A tenant was living in our house in Kolkata since 1963 to 2000, then he moved to a flat he purchased in that locality, but did not hand over the rented flat to us. Then he sub-let the flat to another family. Then the original tenant died in 2008. Since then Rent is not collected and Bill is not given. Finally the sub-letee family left the flat in April 2012. But the son of the original tenant has kept the flat under lock-n-key and refuses to hand over possession. We have contacted the police but they said that they cannot interfere. I cannot force open the doors even in my own house. The flat is empty. What can I do to get possession of my house?