Series of bucket-killing murders happening in the city. Failure to resolve by police, a team of CBI Officers under CBI officer Sethurama Iyer take up the investigation to resolve the never experienced mystery.
CBI 5: The Brain is a 2022 Indian Malayalam-language mystery thriller film directed by K. Madhu and written by S. N. Swamy. The film stars Mammootty reprising his role as CBI officer Sethurama Iyer along with an ensemble cast. It is the fifth installment of CBI film series.