The Mutya ng Pasig tagalog movie was adapted from Nicanor Abelardo's poetical song inspired by the immortal kundiman and was spearheaded by his brother Richard Abelardo. The movie tells about the supernatural melodrama of a woman's misfortune and suffering interwoven with the legend of the Pasig.
Mercedes (Rebecca Gonzales), aside from being the town's current mutya (fiesta queen), is about to be married to his childhood sweetheart. (Roger Nite). Unknown to them, Dr. Modesto Millar (Jose Padilla Jr), is also secretly in love with Mercedes. One night, Modesto's house is robbed and the blame is placed on Mercedes' groom-to-be. He is arrested and imprisoned after which Modesto courts Mercedes and eventually marries her. When the former fiance is finally released, gossip spreads about hi m and Mercedes.
Consumed by anger and jealousy and believing the superstitious talk that the baby girl is not his because of an ugly birthmark, he banishes Mercedes and the child, chased by his monstrous dog, and she drowns in the river. From that point on, a legend spreads about a woman, a sirena, haunting the river singing a sad but beautiful song.
