Set in a secluded Tulu village on the Kerala-Karnataka border, Muthassi follows Leela, a devoted mother caught between love and horror when her only son, Sreekuttan, begins to change in strange, terrifying ways. After her husband Rajan's mysterious return to their ancestral home, suppressed secrets of blood rituals, demonic ancestry, and a cursed family legacy begin to surface. The village, surrounded by dense forests and age old myths, becomes the backdrop for a chilling spiritual battle between motherhood and monstrous destiny. As Sreekuttan undergoes a terrifying one day transformation linked to a demonic ritual once performed by Rajan's mother Kaanti, Leela discovers the horrifying truth: her son is not entirely human, but the child of a Rakshasi. With each passing day, her son's behavior turns violent and unnatural, while ghostly apparitions haunt their home. Leela must navigate a nightmarish past involving Rajan's betrayal and Kaanti's unholy powers, even as ancient village superstitions begin to come true. Every choice Leela makes becomes a fight against time, myth, and maternal fear.As the final night of the transformation nears, Leela faces an impossible choice: destroy the child to save others, or accept and protect the demon he's becoming. In a powerful emotional climax, Leela chooses love over fear, confronting the evil within her family's bloodline with the strength only a mother can summon. Muthassi ends not with closure, but with a lingering question can a demon be raised with love, or will darkness always claim what it birthed? This is a story where horror meets heartbreak, and where mythology becomes painfully personal.