The story is set in the backdrop of the slums of Pudhupettai in Chennai, as the title suggests, where a high school kid Kokki Kumar (Dhanush) sees his mother dead after he comes back from watching a film. His father, the murderer, is also planning to kill his son Kumar. Kumar sensing danger runs away from home. Homeless and with no food he resorts to begging until he is falsely arrested while standing by and watching a commotion on the street. In jail he befriends handymen of a local goon who take Kumar with them and give him petty jobs. In a confrontation with goons of another gang Kumar kills the brother of his enemy gang's head Murthy thus earning the respect of his gang and making enemies for himself both within his gang and outside. Krishnaveni (Sneha) is a prostitute who also works under Anbu. Kumar falls in love with Krishnaveni and challenge Anbu to release her. Anbu in return beats Krishnaveni and orders to kill Kumar. Kumar approaches Anbu and asks to pardon him but Anbu wonders if it would be possible cancel the order to kill Kumar. Kumar infuriated kills Anbu and approaches Thalaivar (Azhagam Perumal), leader of Opposition in the state. Thalaivar says if he could survive until the next day morning from Anbu's goon, who is seeking revenge, he would be bestowed with Anbu's area for business. Kumar survives and Thalaivar keeps him in place of Anbu.

Kumar grows even further in the underworld. He kills his father and his hench men. Murthy is stabbed by Kumar's men. Kumar joins Thalaivar's political party for immunity from police and arrests.

He then meets Selvi (Sonia Agarwal) on the eve of her wedding and falls in love with her and marries her forcibly during her wedding ceremony. Selvi is the sister of his favourite henchman who now becomes his sworn enemy and joins the enemy gang. Slowly Kumar starts accumulating serious enemies and eventually everyone start targeting for Kumar's head.

Finally, Kumar kills Murthy (a ruling party MLA and Kumar's sworn enemy) and is arrested, but the incumbent CM sees the high potential in Kumar and brings him out of prison and wipes his record. The CM gives Kumar his party's ticket from the dead leader's constituency in the by-election. Then it is told that Kumar won that election, became an MLA and 10 years later became the Finance Minister of Tamil Nadu. He owns large number of industries and educational institutions. Still his lost son is not found after an exhaustive search.