Nerariyan CBI is a 2005 Indian Malayalam-language mystery film directed and produced by K. Madhu and written by S. N. Swamy. The fourth installment in the franchise of CBI investigative thrillers, Mammootty reprised the role of Sethurama Iyer, a Central Bureau of Investigation officer, with Mukesh and Jagathy Sreekumar reprising their roles as the associate officers Chacko and Vikram, respectively, and the background score composed by Shyam.