Potential buyer fraudulently took property papers.How to get them back

Hello, Before 1 one year my parents took a decision to sell our house to a neighbor aunty and after the agreement my father got expire as a token money she gave 1.5 lac but house is on my mother's name and before expire my father gave original sales deed to that aunty for originality checking and we came to know that after my father got expire now it's been a 14 month that aunty is not giving our sales deed and also she is not purchasing our home also and now she is saying that your father and mother mortgage your home @10% per month intrest so I am not going to buy your home and return my money with all the intrest and we have financial problem so my mother and me want to sell our house asap but we don't have original sales deed and that aunty is troubling us on a daily basis. Please help me.