Punyam movie tells the story of princess Sukanya (Lakshmi Gopalaswami) who agrees to marry the old sage Chyavana (Narendra Prasad), whom she had blinded by accident. Dasran (Boban Alummoodan) and Satyan (Krishna Kumar) who are two Ashwini Kumaras (the celestial physicians) come to the ashram of Chyavana and when one of them tries to seduce Sukanya, she impresses him with her steadfast loyalty to her husband.
Consequently, the Ashwini princes grant her a boon, that of restoring sight to Chyavana and to bestow him with eternal youth. But there is a clause. Chyavana has to take a dip in the Payoshini river with one of the Ashwini princes and when they emerge from the water, they'd both look alike. Sukanya then has to identify her husband.
However, if she picks the wrong person, she'd still have to accept him as her husband! What happens thereafter forms the climax.