Thalainagaram tells the story of a group of compassionate henchmen who, after choosing to leave their violent past behind, face numerous challenges. Right (Sundar C) and Balu (Bose Venkat) serve under a notorious don, Bhai (Judo Rathnam). The arrival of Dhivya (Jyothirmayi), who settles in their neighborhood, sparks new hopes. However, tensions arise when Right clashes with Bhai, resulting in him killing Bhai’s son. In retaliation, Bhai murders Balu, prompting a change of heart in Right and his men. Determined to lead honest lives, they attempt reform, but their plans are thwarted when a corrupt cop, Prakash Raj, forces them back into violence. Bhai then relentlessly pursues Right, leading to a series of confrontations involving Bhai, Right, and Gopinath. Ultimately, Right emerges victorious in this turbulent struggle.