Oru CBI Diary Kurippu

• Mammootty as Sethurama Iyer, DySP of CBI
• Suresh Gopi as Harry, CI of CBI
• Jagathy Sreekumar as Vikram, SI of CBI
• Mukesh as Constable Chacko
• Sukumaran as DySP Devadas
• Janardhanan as K. A. Ouseppachan
• Prathapachandran as Narayanan, Politician
• Lissy as Omana John Thomas
• Urvashi as Annie John Thomas, Omana's sister
• Bahadoor as John Thomas/Thomachan, Omana's and Annie's Father
• Sreenath as Sunny, Omana's Husband and Ouseppachan's Son
• Vijayaraghavan as Joy Mathew / Johnykutty, Ouseppachan's Son In Law
• Captain Raju as DySP Prabhakara Varma
• Jagannatha Varma as SP, CBI
• K. P. A. C. Sunny as C.I Alex
• C. I. Paul as Minister Bhargavan
• Kollam Thulasi as Police Surgeon
• Poojappura Ravi as Padathalam Mathai
• Adoor Bhavani as Mary
• T. P. Madhavan as Sreedharan
• Kundara Johny as Driver Vasu
• Sukumari as Nun
• Kothuku Nanappan as Mohammed

The Central Bureau of Investigation (CBI) led by Sethurama Iyer investigates an enigmatic murder that was made to look like a suicide.

The movie opens with DySP Prabhakara Varma observing the local police force during a training drill. Another officer approaches him and informs him that he is needed at a recent crime scene, and they depart immediately.

Varma arrives at the home of Ouseppachan , a local businessman, and sees the body of Ouseppachan's daughter-in-law, Omana on the grounds behind the house. He then interrogates Omana's husband Sunny, her father-in-law Ouseppachan, Ouseppachan's son-in-law Johny , Ouseppachan's best friend Narayan, and several of the household servants and neighbors. The initial report conducted by the first responders concluded that Omana had committed suicide by flinging herself from the roof of the two-story house onto the stone pavement below. Varma questions the neighbors and servants about Omana's relationship with her husband Sunny. Sunny admits to arguing with Omana the night she died and pushing her onto their bed before leaving to drink, but swears he never hit her. He also tells Varma that Omana had attempted suicide before. Ouseppachan claims he came home from a business trip that night, dropped off by his driver, Vasu, only to find himself locked out of the house. He decided to go around the back to where the cook's quarters were located when he stumbled upon Omana's body. Dissatisfied with inconsistent testimonies from several suspects, Varma immediately suspects foul play and is determined to find the truth.

The next morning, the Regional Medical Officer concludes that Omana died from head trauma at 8pm the previous night.

Omana's cousin Chacko, a police officer working under Varma, notices Ouseppachan commending one of the servants for something suspicious. He also finds the autopsy report suspicious and tells Varma and Officer Alex why he has doubts to its accuracy. He informs them that it rained severely until 9:30pm the night Omana allegedly committed suicide, and if she had died at 8pm, her corpse would have been wet, and the blood from her injury would have been mixed in with the rain water. Alex, who is taking bribes from Ouseppachan, warns Ouseppachan to do what he can to get Varma and Chacko off the case.

Sensing that Varma will cause him trouble, Ouseppachan implores his best friend, Narayanan, a local politician, to call his politician friends (including the Minister) to have Varma transferred off the case. They also managed to take Omana's cousin, Chacko off the case as well. A new DySP Devadas, takes over the case. Devadas, who is also being bribed by Ouseppachan, intimidates Omana's grieving family and any witnesses that may implicate Ouseppachan or Sunny. He quickly concludes the investigation stating that Omana committed suicide.

Omana's father Thomachan and her sister Annie are determined to seek justice for Omana. Chacko helps them take the case to the CBI. The Director of the CBI assigns CBI DySP Sethurama Iyer to head the investigation. He is assisted by CBI Circle-Inspector Harry and CBI Sub-Inspector Vikram.

Iyer asks a few questions to Thomachan and Annie regarding Omana and her relationship with Sunny. Ouseppachan was very close to Thomachan during Omana and Sunny's nuptials, and everything seemed golden at the time. However, the trouble started after Ouseppachan refused to pay back some money that Thomachan loaned him, even after he built a big business and could repay it easily. Omana attempts suicide in March for unknown reasons and dies in June of that year. Iyer then goes on to ask Chacko about why he decided to take the case to the CBI. Chacko states his suspicions (the same that he said to DySP Varma), which Iyer finds convincing. Chacko is attacked en route from the hotel where Iyer is staying by driver Vasu and his gang. Iyer says that the incident had "accelerated his doubts in this case."

Iyer and his team plan three stages of the investigation. First; whether there was any corruption in any of the evidence, second; whether or not Omana's death was a murder or suicide, and if so, who did it.

Iyer and his team commence the investigation and find evidence of political interference in Omana's murder investigation. They cite an increased amount of phone calls to Ministers and Party Leaders from Narayanan's phone number, and thousands of rupees worth of cash withdrawals from Ouseppachan's bank that were never reported in the books. Iyer meets with Varma and Chacko who help him with his investigation by informing him of inconsistent testimony from suspects and the inconsistencies with the Regional Medical Examiner's autopsy report. Later that week, Iyer and his team bring two dummies the same height and weight as Omana to Ouseppachan's house. They take the dummies to roof and drop one straight down as if it jumped, and threw the other off the roof as if someone had thrown the body. They find that Omana's body landed approximately the same place as the dummy that was thrown, and concluded that she could not have jumped that far off the roof on her own. Next, they decide to track down Ouseppachan's driver, Vasu, who has been missing since the morning after Omana's death. Harry finds out that Vasu had given a local banker some jewelry as collateral for a loan. Among the jewelry was a bracelet belonging to Omana, which immediately put all suspicion on Vasu. They finally find him and take him into custody, where he confesses that shortly after he got home after dropping off Ouseppachan the night of Omana's death, Narayanan came to his house and told him that Sunny had accidentally killed Omana during a domestic dispute. Vasu then said Narayanan and the others implored him to carry Omana's body from her bed to the roof and fling her off. It was during a moment alone with Omana's dead body that Vasu had noticed her gold bracelet and decided to steal it, before throwing her corpse of the roof.

Despite Vasu's testimony implicating Sunny as the killer, Iyer is not convinced. Sunny had left the house at 8 pm after hitting Omana and that would mean that she died at 8 pm. However, Iyer examines photographs of the crime scene and finds that Omana still bled when she was dropped off the roof some 2 hours later, and since dead bodies do not retain heat thus causing the blood to clot, she could not have died at 8 pm. Upon scrutinizing the photographs further, Iyer notices a small blood stain on Omana's saree below the waist. Since the autopsy report stated that she sustained no injuries below the waist, Iyer is convinced that the blood was left behind by the real killer.

After testing the blood they find that it is O-negative, a rare blood type. Remembering that the town had imposed mandatory blood tests on all its citizens recently by the local authorities to combat malaria, Iyer goes to the Malaria Research Center and finds that the blood type was so rare that only three people in the entire town had it.

In the final scene, Iyer arrives at Ouseppachan's house with a large police backup unit and places Ouseppachan under arrest for the murder of Omana. Shocked, Ouseppachan vehemently denies killing her, but Iyer would not relent. Seeing his father being arrested for a crime he committed, a guilt-ridden Sunny confesses to Iyer that he killed Omana accidentally by hitting her too hard when they fought. Iyer tells Sunny that Omana did not die when he hit her, that she only fainted. Iyer then goes on to explain the blood on Omana's saree, which did not match her own, was left behind by the real killer. He informs them that only three people in the entire town were O-negative and one of those three people is Johny, Ouseppachan's son-in-law. Confronted with evidence for his involvement, Johny confesses that he had come to the house the night Omana had died. Finding her passed out on the bed, he attempted to rape her, but when she woke up and started screaming, he suffocated her to death. In the process he accidentally cut himself and left his blood on her saree.

Thomachan and Annie thank Iyer, Harry and Vikram for their hard work and dedication and bringing Omana's killer to justice. The movie ends with a reference to Sukumara Kurup, a real life notorious fugitive wanted in India for murder, who to this day is still on the run.

Oru CBI Diary Kurippu was a commercial success at the box office.[6][7][8] It collected around ₹2 crore (US$280,000) from theatres.[9] The film had good reception in Tamil Nadu.[10][11] It ran for 210 days at Safire theatre in Madras.[12]

• Mammootty's Sethurama Iyer was initially conceived as a Muslim character, Ali Ibrahim, but Mammootty suggested an Iyer character to incorporate jibes of Devadas (Sukumaran) about vegetarianism and lack of Iyers to do physical work. This resulted in one of the most popular two-character confrontation scenes between Sethurama Iyer (Mammootty) and Devadas (Sukumaran). Due to its popularity, this was repeated in the sequels Jagratha and Sethurama Iyer CBI. The third sequel was released 15 years after Jagratha. By this time, Sukumaran, who had portrayed Devadas, had passed away. Thus, Saikumar was cast as the son of Devadas; he was required to mimic Sukumaran's style of performance.
• The film concentrate on the central investigative story only, without the songs and dances generally associated with Indian commercial films.
• The plot-line of the film was crafted around the real life Polakkulam Case in which a hotel employee was murdered and dropped from the terrace to make it look like a suicide. It was also the first case where a humanoid dummy experiment was conducted in the state of Kerala to prove the murder.

• Oru CBI Diary Kurippu at IMDb