Declaration and Injuction Case filed in Our site

Sir, I had purchased a site from the Previous Owner Mr A in Oct 2009 through a registered sale deed. Mr A had Purchased the same site from Mr B who was the GPA (Notary) holder of Mr C (The first Owner) on 23 Feb 09. Mr C had got this land issued from Govt in 1975 for 25 years of Independence. Now after i registered my property on 09 Oct 09, Mr C's Son has filed a case of declaration and injunction on 12 Oct 09 on my previous owners stating that they forcefully threw them out of House and took charge of the property. He claims that his father gifted them the property thrugh registered deed on 09 Feb 2009. However his father Mr C had already given GPA (Notary) to Mr B in June 2008 on the basis of some money taken as credit from Mr B. Mr C's Son has produced only the giftdeed in the court however i have all the documents from Hakku Patra (Govt Issued Patta) to Mr C, The GPA and the succeeding sale deeds. Now after i purchased the site i have demolished the sheet house and constructed a new house (2 floors) and in possession of the same for last five years. ALthough he had a stay with him he came with police only during the last stages of House completetion. I Have already invested 30 lacs in this Plus site. Kindly guide me how the case will proceed . Am really worried.