Guess what , mammooty is back again with CBI series . His fasn haven’t forgotten the character Sethurama Iyer CBI which was a milestone in his acting career of Megastar Mammootty . Director K Madhu and script writer SN Swamy who has done the prequels too is gearing up for the next installment in the series . It would be titled Black Investigation . Out of four prequels , the first 3 were chart toppers and the last one was a mild success . Sources reveals that K Madhu would start working this project after the completion of his film Banking Hours 10-4 with Anoop menon and Meghna Raj . SN Swamy is working on the script for the last one year as he has to make it foolproof. Hope he has got something new under his sleeves and would rejuvenate the series .