The Morris family just wanted a fun summer vacation, but a wrong turn leaves them completely lost. Just when they are about to give up, they spot a massive billboard for an amusement park they have never heard of: HorrorLand. Luke and Lizzy Morris are excited to stretch their legs and check out the rides. But this is no ordinary theme park. There are no joyful clowns or cotton candy stands. Instead, they find terrifying attractions like Werewolf Village, the Doom Slide, and the terrifying Coffin Cruise. The park workers are dressed as monsters, and they never seem to break character. At first, the family thinks it is all just amazing special effects and spooky fun. But as the rides become more dangerous and the park gates suddenly lock, Luke and Lizzy realize the horrifying truth. The monsters are real, and they might never get out!