Mortgage property is purchased without knowing.

My father purchased a property in Kolkata. After staying for 4 years we came to know that the property is mortgaged with some bank. But we have original papers of flat. The mortgage loan was taken by husband of the 1st purchaser. We are 3rd in number. We purchased from 2nd purchaser. Some bank people came and told us. Now what to do.what will happen to our property. What can bank do.My father purchased a property in Kolkata. After staying for 4 years we came to know that the property is mortgaged with some bank. But we have original papers of flat. The mortgage loan was taken by husband of the 1st purchaser. We are 3 rd in number. We purchased from 2nd purchaser. Some bank people came and told us. Now what to do.what will happen to our property. What can bank do.My father purchased a property in Kolkata. After staying for 4 years we came to know that the property is mortgaged with some bank. But we have original papers of flat. The mortgage loan was taken by husband of the 1st purchaser. We are 3 rd in number. We purchased from 2nd purchaser. Some bank people came and told us. Now what to do.what will happen to our property. What can bank do.