How To Save My Mother-in-law From Daily Domestic Violence And Clashes?

My unemployes brother-in-law (40 years) and her homemaker wife forcing my widow senior citizen mother-in-law to register her owned property in their name, transfer all her savings to their accounts and give all from her monthly family pention. They both are dependent still on my mother-in-law. They make her do all household work in this old age. Wife of my brother-in-law threatens her of false dowry aligations and jail. They also threatened her of dire consequences if she tells the matter to anyone or to her daughter (my wife). They live in Rajasthan and we in Delhi and we came to know all this from their neighbours and our common relatives. My wife is worried about her safety and respect. They don't have any child even after 13 years of their marriage. Any suggestions...