problem relating to land

friend i need advice. m in deep trouble. i purchased a land one year ago. have all the registered documents. bt recently i came to know dat someone else is also holding the registered documents of the same land. the matter is dat the owner of the land sold it twice (to me and the another person) now the owner is not cooperating and he has political source as well so i m not getting any help. the another person to whom the land is sold says dat as the land was first sold to him he is the actual owner. frns i m very much depressed please let me know if there is any remedy. please help