Ravana Prabhu movie begins with the fall of Mangalasherry Neelakantan's (Mohanlal) son Karthikeyan (Mohanlal) ventures out to make money which ultimately makes him a booze baron. Relationship between Neelakantan and Karthikeyan deteriorate, as the father does not approve his son's money making methods.
Shekharan (Napolean) comes into the picture again after spending a term in prison for killing one of Neelakantan's friends. He decides to finish the Mangalasherry family by confiscating the house which was kept as collateral for Bhanumathi's (Revathi) treatment.
Bhanumathi passes away and Karthikeyan is now bent on taking revenge. Neelakantan loses his home and Karthikeyan ventures out in an attempt to reclaim his ancestral home. In the mean time, Karthikeyan abducts Shekharan's daughter Janaki (Vasudara Das) in an attempt to blackmail him(Shekaran) during which they fall in love with each other.
The remaining part of the movie is about how Karthikeyan manages to get his ancestral home back while Shekharan's nephew makes attempts to kill Karthikeyan.