Bank done fraud in loan papers what to do now

My father in law got a loan against a property in 2001, then he sold that property to a person along with the loan being transferred to his name as he wanted. The bank manager played a conspiracy along with him and gave the cheque back to that person which he paid to bank along with original property papers saying NOC will be given to him as he is the owner now, this happened in 2001. Now in 2011 bank issues notice against my father in law saying that he has done fraud and not paid loan amt. Bank is not able to find registry papers but only has the loan papers. No NOC copy nothing. And now they come to my another property saying that they will recover that property which had nothing to do with the case. I really need urgent help as the bank says we can solve the issue with 15lacs.And ofcourse we cannot provide that amount. They dont show any copy of any legal papers saying that this is legal we cannot provide it to you. What to do?