A tale that blends mythology and present times, Panchamirtham begins with Ravana (Prakashraj) asking his brother Mareesan (Jayaram) to transform into a deer and abduct Seeta. Mareesan finally agrees, unwillingly, when Ravana and Idumba (Raju Eswaran) threaten to harm his lover.
As is obvious, he is shot by Lord Rama and gets transformed into a rock but not before he transforms Idumba into an anklet and wears it on his leg.
Now the story moves into the present times where Rajaram (Nasser) is a rich man who owns tea estates and his dietitian Seetha (Saranya Mohan) and his cook Sri Rama (Arvind Akash) are in love. But his relatives want to acquire his property.
Thus they plan to kill Seetha who is pushed off a cliff. She falls on the statue of Mareesan and he comes into his human form. In a series of events that follow, Idumba also comes into his human form and then continues the rivalry where Mareesan vows to protect Seetha and Idumba supports the relatives.