Aiwan-e-sadar. Owner died and a fraud case. Please advice.

I purchased a plot here in aiwan-e-sadar in early 2000's. At that time the transfers were not opened, so i bought the file and kept it with me. Now when i heard about the open transfers, i went to society office and they have told me, the plot is not on your name, but i showed them that original file is with me.
So the case was, the original owner died and her widowed wife used his death certificate to claim for a duplicate file and sold it to some one else. Now the society is not cooperating and even the widow and her son are not saying anything about that, please advice what can i do?

Do a case against the window and the society both. The window committed fraud and the society.

Open files I don't think exist anywhere in the world and I think the purpose of these is to rob people usually with connivance of the housing societies themselves.