The CBI film series is a series of four Malayalam films directed by K. Madhu and written by S. N. Swami featuring Mammootty as Sethurama Iyer, a Central Bureau of Investigation (CBI) officer. The series started off in 1988 with the block buster Oru CBI Diary Kurippu. The films depicts a team of CBI officers led by Sethurama Iyer investigating into a murder case.
Prabhakar Varma is appointed by the police to investigate the suicide of Omana, the daughter-in-law of a businessman. Varma decides to investigate further when all the clues reveal it was a murder.
A renowned actress, Aswathi, is murdered. When a CBI officer, Sethurama Iyer, investigates the case, he unravels a dark secret about Aswathi which brings forth several complexities.
Alex, who is awaiting execution, confesses to having committed six out of the seven murders he is acquitted for. Officer Sethurama Iyer decides to trace the original murderer of the seventh one.
A string of mysterious murders happen in an aristocratic mansion. The owners of the mansion seek CBI officer Sethurama Iyer's help to find the person responsible for the deaths.
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.
