Land fraud deal

One of my close cousin transferred 40 lakhs in my account as he was buying a property in my city. The registered agreement was done at registrar office and now after few weeks we came to know that the whole sale deed was fraud and the person from whom it was bought is missing and property papers shown to us were also bogus.No due diligences was carried out by him and now it has all become a big headache. In sheer desperation he is now planning to file a case of 420 against me saying that is what his lawyers are advising him and then I will have to file a case against the guy who sold property as all cheques are signed by me( since money was transferred in my account ). Please advise.