The series revolves around a 12-year-old girl named Emily Hayes and her younger brother Navin, and the elf prince Trellis. Two years after the death of their father in a car crash, their mother Karen Hayes moves to the kids' "dead" great grandfather's house. When their mother is kidnapped by an Arachnopod, the two siblings pursue her through a small door in the basement that leads them to an alternate fantasy version of Earth, called Alledia.