Blackmailing / cheque bouncing

Sir/Mam, There is a need of legal advice as the case is,I have given one lakh rupees to one of the person for some medical issue of his family and that person is my client/customer,As I am working in a Stock Broking company and he has opened his dmat & trading account in our company last year and due to this our relation grows up by day to day meeting in my office as hi visit was on daily basis during market hour.Last year I have sold my home town village land and planning to buy a house from that amount last year as he know many good brokers of land that's why I have asked him regarding planning to buy house in a city.After one week suddenly he requested me to give him one lakh rupees for some medical urgency /operation for his wife as he know ver well that I had fund at that time,I have given him and asked to do notarised agreement for this amount and he was agreed and made a notarised agreement for this,After three months I have asked to refund my amount then he is taking me lightly and always replied me you will get it soon don't worry for that.And the main turning point is that one day I have searched my Axis Bank cheque book in my office drovers as I always keep my unsigned cheque book and important documents in my office table drovers and that cheque book was of my previous company salary accounts cheque book as I have not done done any transactions after leaving my previous company and I was totally shocked when I couldn't able to find that chequebook in my drovers,I have visited Axis Bank and narrated regarding missing of my cheque book and given application.for stop payment but they were not accepted that because my axis bank account was running in minus 8755/- and that bankers was asking to deposit that minus amount then only they will ready to accept stop payment request of all cheques,then after getting this reply from banker I have lodged a FIR in nearest police station,one day I have got a call from city kotwali and that police person was told me that there is a FIR lodged against you for 420 and told me the person name who has lodged it and the person name was same whom I have given amount as a loan,that police man asked me to come to police station and told me that you have given him cheque but that cheque was bounced after listening this I have narrated all the things which I have mentioned above but he was using unusable words and ask to come there,By this incidence it was completely confirmed that the person who has stolen my cheque book was the same person whom I have given the amount as a loan ,Now the matter stands that person is doing blackmailing me and doing mentally harassment and telling that I am not going to refund you the amount do what ever you will do,and also telling me If I will ask for refund of that amount then he will do case and by using his source police will arrest me,I am totally disturbed and cant able to see any path,please guide me what should I do and how I will get back my money from him....... Thanks & Regards Mahesh Kumar Baghel