Vallamai follows Saravanan, a hearing-impaired single father who moves to Chennai with his young daughter, Boomika, in search of a better future. Saravanan works tirelessly as a poster-sticker to make ends meet while nurturing dreams of a secure and happy life for his daughter. However, tragedy strikes when Boomika is subjected to horrific abuse, forcing Saravanan to embark on a painful and emotional journey seeking justice and redemption.