Arunachalam starring by rajinikanth and soundarya. Rajnikanth finds himself to be an orphan by interval. He goes out of the village. He goes to Madras where he meets Janakaraj, who gives him a job. By some magical situation Rajni discovers himself to be a son of a (dead) millionaire - through Visu.
Visu is the guardian of Rajni's father's trust. If Rajni wants his inheritance, he has to follow certain rules. He can get an inheritance of $1 billion if he can spend $10 million in a month. The conditions are: no contributions to charities, not to own any assets at the end of the month and above all, no one else should know about this! Receipts should be provide for all the expenses.
If Rajni fails to spend the money according to the rules, all the money will go to his father's trust which is managed by V.K.Ramasamy, "Nizhalgal" Ravi, Kitty and Raguvaran. These four form a team of "villains". They want to spoil Rajni's efforts and get all the money for the trust and kill Visu. Rambha is Visu's daughter and she is appointed as the accountant for Rajni for 30 days.
What happens next is the main part of the story. Rajni tries hard to spend his money and many times, the money comes back! He spends on Horse races, lottery tickets, makes a movie with Senthil as the hero and he even starts his own political party with Janakaraj being the candidate.