Thirteen-year-old Lacey Berge is furious. Her dad's dragged her to her late great-uncle's mansion in the mountains of Vermont, and taken her stepsister Cal along for the ride. Lacey can't stand that little know-it-all, and nothing her dad can say or do will force them to bond.

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But soon after the arrive, an emergency forces Lacey's dad to leave the girls on their own. When they take the opportunity to explore, they discover a secret lab and accidentally open a portal to another dimension, unleashing a horde of mischievous monsters into the mansion!

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Can these reluctant siblings put aside their differences long enough to

get rid of the creatures before Lacey's dad gets back?