Thanks to unexpected events, 12-year-old Tim and his sisters, Sarah and Jenny, are left on their own at the family's summer cabin. It seems like a dream come true. Tim can spend all his time training for the upcoming big race. And 13-year-old Sarah can read about vampires and collect butterflies to her heart's content.
But the dream soon turns into a nightmare. Bats -- hundreds of them! -- have invaded the house. Meanwhile, the kid in the house next door is wasting away, haunted by bloodcurdling dreams. When Sarah-develops the same symptoms, Tim realizes the bites on their necks are not from mosquitoes. Vampires are loose in Starfish Harbor. And Sarah's about to become one of them... unless the kids can find and destroy them fast!