GIRL VS. MONSTER centers on 15-year-old Skylar (Olivia Holt), a typical teen who bemoans her parents' strict rules about curfew. Even worse, they forbid her to leave her house on Halloween night when the greatest party of all time is happening in a decrepit nearby mansion and her dreamy classmate Ryan (Luke Benward) has asked her to sing with his band onstage. But when she rebels and sneaks out to go to the party with her friends Sadie (Kerris Dorsey) and Henry (Brendan Meyer), she inadvertently sets free a collection of monsters her parents had contained in the basement, including the immortal Deimata (Tracy Dawson), who has her sights set on revenge against Skylar's family. Suddenly Skylar must come to terms with the fact that her parents lead a secret life, that she herself is a fifth-generation monster hunter, and that it will take all of her courage to face down fear and recapture Deimata and her gang.