एक ही जमीन की दो बार रेजिस्ट्रिया हुई।

If the same property was sold to two different parties then the subsequent sale of property would be invalid. 

File a police complaint for committing cheating and fraud upon the buyer.

Get the subsequent mutation cancelled by filing an appeal before concerned revenue authority.

If you are one of the party to the transaction file a suit for cancellation of subsequent sale deed.

Contact, consult and engage a local prudent lawyer for proper analayses of facts / documents and advise / necessary proceeding.

I'm not a legal expert, but I can try to provide some general information that may help. If you suspect an illegal mutation on a property title, it's essential to seek legal advice from a qualified attorney specializing in property law. They can guide you through the process and help you understand your rights and options. In general, mutation is the process of changing the title of a property from one person to another. However, if this process is done illegally, it can lead to serious consequences. Some steps you can take include: 1. Verify the property records: Check the property records with the relevant authorities to ensure that the mutation was done legally and with the consent of all parties involved. 2. Consult a lawyer: Reach out to a qualified attorney who can review the case and provide guidance on the best course of action. 3. File a complaint: If you believe that the mutation was done illegally, you can file a complaint with the relevant authorities, such as the police or the revenue department.

The question is, who is in possession and occupation of the property?