Aanaikundram Jail. Superintendent K. Raghavan is a man of integrity and humaneness who views the 500 inmates as 500 books that need to be perused. He stays with his wife Alamu in the bungalow adjoining the penitentiary, and the childless couple treats the prisoners with compassion and love, for they look upon the inmates as the children they never had. Chamundi who is serving a life sentence for killing one of the 2 villains who had fatally molested his teenaged daughter Sivakami, Syed who , Kesavan who ensures that he is arrested ever so often on trivial crimes, for he prefers the comforts of the prison to the uncaring outside world…. With the unusual backdrop of a prison, JK endows each character with an interesting history and subtle idiosyncrasies.
Kai Naattu is the story of a goonda who always stands for justice. He had his dreams to have a peaceful life, but society turned him a goonda. His only pleasant memories are the time spent with his lady love.
The film begins with the robbery of a bank by a terrorist group. Each member of the terrorist group works in various sectors, but above this, they need money. Prathap (Mohan) and his friend Sri (Charle) are petty thieves. One day, Vidya (Divya) falls in love with Prathap. Vidya's brother Subash (Kitty) cherished her. When he knows about her love affair, he doesn't hesitate to kill her only because it's against the terrorist group's rules.