In a small, rural Filipino village, a family is haunted by an ancient curse known as "usog," a supernatural affliction brought by an aswang—a shape-shifting creature in Filipino folklore. The curse affects their youngest child, Maris, who suddenly falls ill after a stranger visits their home. Her family suspects the stranger is an aswang who cast an usog on the child, leaving her weak and tormented by strange dreams.

Desperate to save Maris, her older brother, Datu, seeks help from the town’s albularyo (healer). The healer warns them that the aswang will return at the next full moon to claim Maris. Datu must gather his courage and learn ancient protective rituals to fend off the creature.

As the full moon rises, the aswang takes on terrifying forms, trying to breach their home. Datu and his family must fight to protect Maris, using everything they’ve learned about the creature's weaknesses. In a dramatic showdown, they confront the aswang in a final battle between ancient magic and modern resolve.

The story combines elements of Filipino folklore and usog superstition, offering a tense, chilling tale of family, fear, and survival.