Power of attorney cheating and plots are sold

Sir , my grand mother having 4 acres land at caddalore and she maintained the land up to 1983 , after that she settled in Chennai and she gave general power of attorney to one person in caddalore for convert this land to plots and execute the sale , but she mentioned in power specifically like POA not having rights to register the plots and he should maintain the account for sale and handover to my grand ma. But he is not act as per power and he was cheated my grand ma like actually the power was given 1984 August but he sold some plots in 1984 March and my grand ma was died in 2008 but he sold so many plots after his dead. We taken EC from 1960 to upto date .He sold all plots and most of is after dead of my grand mother.Now what we do. Please advice to us for this problem