Thenum Paalum is a story of Ramu (Sivaji Ganesan),Janaki (Padmini) & Thangam (B.Sarojadevi). Ramu goes to meet his father's old friend who is an advocate & has vacant plots on which Ramu wants to build a factory for his company. There due to unforeseen circumstances he ends up having a physical intimacy with Thangam & has no option but to get her back to his town. He makes her stay in his guesthouse while he stays with his wife Janaki,son & Mother-in-law. Thus begins the hide & seek story of Janaki,son & Mother-in-law. Thus begins the hide & seek story of Ramu & his 2 wives.