Avvai Shanmugi

Five years into their marriage, Janaki files for divorce from Pandian, citing their growing emotional distance, Pandian's long work hours, and the cramped, unsatisfying home. The divorce is granted, setting the stage for Bharathi's custody arrangements and Pandian's limited access.

Janaki is awarded sole custody of Bharathi, while Pandian can visit only once a week. This arrangement leaves Pandian longing for time with his daughter, and Bharathi becomes attached to him despite the separation.

Basha counsels Pandian to steal Bharathi to be with her; Pandian agrees, but their plan is discovered, resulting in him losing his access completely. The breach deepens the rift between father and daughter and their protectors.

Pandian learns Vishwanathan is advertising for a nanny; he confides in Joseph, a makeup artist, and they transform Pandian into Avvai Shanmugi, an elderly Iyer woman. This disguise sets the stage for his continued presence with Bharathi and Janaki without revealing his identity.

Shanmugi applies for the nanny position but is rejected when another candidate is chosen. Undeterred, she stays close to Bharathi and Janaki, hoping to influence them from behind the scenes.

Bharathi is injured while fireworks are being shot, and Shanmugi pulls her out of danger and treats the burn. The family doctor commends her handling, convincing Vishwanathan that Shanmugi is capable of caring for Bharathi.

Impressed by Shanmugi's care, Vishwanathan drops the earlier nanny and hires Shanmugi permanently, and Janaki and Bharathi begin to form a bond with their new guardian.

Rathna loves Pandian but is ignored; Basha moves in as a mute Iyer cook after Shanmugi's recommendation, but is nearly caught during namaz by Sethuram Iyer, complicating the ruse. Humorous misunderstandings follow as the truth lingers just out of reach.

Mudaliyar, the owner of Pandian's building, bumps into Shanmugi and sympathizes with her, gradually developing a liking for her. This adds another layer to the web of identities and affections surrounding the family.

Pandian realizes Janaki has not forgotten him. Shanmugi rebuffs Vishwanathan's proposals by claiming her husband is alive, while Pandian tells Sethuram Iyer that Mudaliyar is Shanmugi's husband, leading to a tangle of mistaken identities.

Shanmugi confronts Basha and reveals her true identity as Pandian by removing her disguise, but Janaki witnesses the scene and misreads it as seduction, fueling jealousy and tension between them.

Janaki goes to Pandian's house to reclaim him but, seeing Rathna and Shanmugi's clothes, fears infidelity and drives to a bridge to jump into a river. Shanmugi saves her and reveals that she is Pandian, ending the misunderstanding.

Janaki and Pandian reconcile, while Pandian 'kills off' Shanmugi by claiming she died saving Janaki. The ruse resolves the chaos, allowing the couple to be together again and bringing closure to Shanmugi's presence.