Fake registration of plot

I brought a plot form A and got registration and mutation in the very same year A had brought it form B but Mr B was not the real owner of the plot, the real owner of the plot was dead two five years back. The real owner made a registered will to his daughter but due to some reason that will was dismissed. Mr B made a fake statement that he had lost the original registry and got some fake documents with the help of Patwari and sold the plot to A. I took a loan from a bank and constructed a house. But unfortunately where I made my house that was not the same plot which one sold to A by Mr B with some fake documents. At present where is my possession that is another plot and very obviously the true owner of the plot is the different one now he is demanding money form me by saying that it was his plot. When I applied loan the officers of the bank made their all legal quarries regarding plot and issued me all the four instalments time to time. I constructed the building. Now a suit has been filed by B's daughter to get their mutation back because she was a legal heir of the said plot. No doubt her plot is in her possession she made it clear in suit but demanding mutation back which is at present on the name of concerned bank. The bank is saying that it is the very same plot where the bank officers visited and verified the person as a owner. Now I am living in the same house and possession is under me and all the essential connections are registered on my name. After selling the plot to me, Mr A had registered an FIR against B to save himself I think Mr knew the reality. But I was not aware otherwise I did not construct the building there I have invested a huge amount on it. Now how can I get rid of this tension and which type of legal action I should take to save my house.