In this spinoff to the New York Times–bestselling Goosebumps series, a tween controlled by a Halloween mask goes to a theme park to escape the terror.

What should Carly Beth be for Halloween this year? TERRIFIED! Late at night, an ugly green mask is mysteriously calling out to her, and ugly green masks don't like to be ignored. If Carly Beth survives the night, even a scary theme park might sound like a vacation. Or maybe not! At HorrorLand, every night is Halloween. And those monster masks she discovers in the gift shop? They aren't masks.