Theera Kaadhal follows the story of Meera and Raghav, two ex-lovers who cross paths after several years. Meera is now married to a wealthy businessman and has a daughter, while Raghav is a divorcee and works in a corporate company.
Despite their current situations, the two cannot help but feel attracted to each other again. They begin to meet secretly, rekindling their love for each other. However, they both ensure that their newfound romance does not affect their respective families.
Meera, who is content with her life, tries to resist the pull towards Raghav, but he is persistent in his pursuit. He thinks that they are meant to be together and tries to convince Meera to leave her husband and start a new life with him.
Things take a turn for the worse when Meera's husband finds out about her affair. Raghav, who cannot accept losing Meera, decides to take matters into his own hands. He begins to meddle with Meera's life, causing trouble for her and her family.
The situation spirals out of control, and Meera finds herself torn between her love for Raghav and her responsibilities towards her family. Theera Kaadhal raises questions about the complexities of love, loyalty, and commitment.