Rajamanikyam movie is all about Young Muthu’s (Mammootty) widowed mother marries a rich man Rajaratnam Pillai (Saikumar) who’s wife is dead too. His son from the first marriage Raja Selvam (Manoj K Jayan) refuses to acknowledge the new step-mother & is always bitter.
Meanwhile Muthu’s mother, scared of Rajaratnam’s reaction, refuses to acknowledge Muthu as her son infront of her new husband. Angry Muthu does not budge and demands his mother back. Impressed by his guts, Rajaratnam nicknames him Rajamanikyam and develops a soft corner for him.
Unfortunately Muthu gets falsely accused in a child’s murder and flees the village. The years pass by. Rajaratnam’s business flourishes and his greedy daughter from the second marriage Rani (Sindhu Menon) who is always at loggerheads with an equally selfish Raja Selvam to control the vast wealth.
Tragedy strikes when innocent Rajaratnam gets framed in a famous politician’s murder by son Selva with help of cunning Nadar (Ranjith) and is imprisoned. Shocked, he dies of a massive heart attack.
However, the trouble does not end for his rivals because Rajaratnam had already willed Rajamanikyam as the sole decision-maker of the entire empire.
How the illiterate yet street-smart Rajamnikyam, now a wealthy buffalo dealer in Bellary, comes back to the village and takes over while deftly managing the bad guys form the rest of the story.