It's the universe's lucky day: Diana Hansen has finally graduated high school, ready to fulfill her destiny as the youngest, most powerful, and least worryguts of the Keepers who prevent metaphysical disaster. Which means she can take the lead on tackling the little problem she discovers in Kingston, Ontario. Someone has reopened the hole to Hell that Diana and her big sister Claire closed not long ago. And this time, Hell is the local shopping mall. Four acres of air-conditioned chaos means Diana and Claire will need an extended stay in the Otherside to fight through the worst the possibilities have to offer, amid cursed minivans, demonic security guards, and unnecessarily hot elven mallrats. With the Keepers away, Claire's Bystander boyfriend and talking cat will face whatever crawls through the fabric of the universe alone. And when the sisters are separated, Diana's brash confidence and Claire's careful strategy will somehow have to carry the day together...