Thalainagaram dwells on a gang of kind-hearted henchmen who face several troubles after they decide to reform.Right (Sundar C) and Balu (Bose Venkat) work as henchmen to a don Bhai (Judo Rathnam). Enters Dhivya (Jyothirmayi), who settles down in the same locality where Right lives. Meanwhile Right develops a difference of opinion with Bhai. Right ends up killing Bhai's son. Bhai takes revenge by killing Balu. It brings a change of heart in Right and his men. When they decide to reform and lead a decent life, enters bad cop Prakash Raj, who forces them to take up rowdyism again. Meanwhile Bhai is on the pursuit of putting an end to Right.There is series of encounters between Right, Bhai ad Gopinath and finally Right prevails.