In the film, two best friends, Sonny and Sam, find a manuscript in an abandoned house on Halloween night. Upon opening the book, they inadvertently release a bunch of monsters into their small town of Wardenclyffe.
Among the creatures that escape are the evil ventriloquist dummy, Slappy, who is hell-bent on bringing his fellow monsters to life. As the chaos escalates, Sonny and Sam team up with Sonny's sister, Sarah, and R.L. Stine himself, who happens to be living as a recluse in their town.
Together, the group must stop Slappy and his army of monsters before they destroy everything in their path. Along the way, they encounter some terrifying creatures, including witches, werewolves, and even a giant spider.
Despite the danger that lurks around every corner, the trio of young heroes remains determined to save their town and put an end to the chaos once and for all.