CBI 5: The Brain
A series of murders is happening in the city. With the police failing to solve the case, a team of CBI Officers under CBI officer Sethurama Iyer take up the investigation to resolve the mystery.
An anti-government union leader’s only son Sakthivel is arrested by the police to find his whereabouts. They trick Sakthivel into believing them as his well-wishers and release him. When Sakthivel meets his father, the police kill the latter. Feeling betrayed, Sakthivel stabs the police inspector and runs away to Bombay, where he is raised by Hussain, a kind-hearted smuggler living in the Dharavi slums.
One day, when Hussain is ill, Sakthivel, now a young man, decides to carry out the smuggling activity on behalf of Hussain. His demand for a bigger commission from the smugglers makes them furious and they involve a police inspector Kelkar to arrest Hussain and kill him in jail. When they close the case as suicide, Sakthivel is angered knowing the truth and murders Kelkar. He later takes care of Kelkar’s family which consists of his wife and a mentally challenged son Ajit. Kelkar’s wife knew that her husband’s immorality resulted in his death.
Krishna (Jayam Ravi) is a happy-go-lucky youth who excels in every field but always does strange and dangerous things to obtain a certain “kick” – a thrill or excitement that he craves. One such activity is secretly double-crossing his childhood friend Dass (Sathyan) while helping him elope. At this point, he meets Nisha (Tamannaah), who is shocked at his recklessness and writes him off as crazy. Krishna sets his sights on Nisha and woos her in a very unorthodox way; he begs her not to fall in love with him. After a host of comical situations involving Krishna’s caring but easygoing parents (Prabhu and Suhasini), local thugs (John Vijay and Mayilsamy), and an ever-present comic relief Jackson (Vadivelu), Nisha accepts Krishna’s love. However, she sets a condition: Krishna must stay in a well-paying job (he had resigned from other jobs due to lack of “kick”), and only then will she agree to marry him. Krishna accepts but soon resigns again for the same reason and tries to hide it from Nisha. When Nisha finds out, she breaks up with him and leaves him for good.
After losing his wife, Saroj, during childbirth, Erode, Chennai-based Inspector Mukesh Bhargav, brings up his daughter, Kirtika, on his own, rises up to the position of Assistant Commissioner of Police, battles hoodlums, exposes inept and corrupt police officers, as well as investigates politicians, their nexus with senior civil servants, and the underworld, ignoring the fact that his and Kirtika’s days may already be numbered by his many enemies.
The film begins with Arivazhagan (Shirish Saravanan) along with his friend locking up an unknown man and torturing him with a camera filming the whole incident. The movie then turns to a flash back, where Arivu narrates how happy he and his family was. Arivu who is a writer for a press and the eldest son of a retired Police Head-constable and his wife, has a brother named Madhi who is a 1st year Engineering student. Arivu’s Middle-class family life is however happy with his friend Kumar (Sendrayan) mingling as one of the family. Problem begins when Madhi who is pressured by his Girl friend to get an expensive bike, persuades his family to get him a bike. Though hesitant at first, they agree to get him a bike of his choice. However, delay in getting his bike and seeing his classmate Ganesh (Nishanth) spending casually makes him curious to know what he does for money. This is when he is introduced to the heinous crime of chain snatching. Ganesh introduces him to Guna (Bobby Simha) who is heading a gang of young college going chain snatches. Madhi joins the gang and starts to earn through chain snatching, and gets all the things he wants.