About a week after the Woods family move in to Xaos House, their daughter Ellie goes missing during a power cut. The odd thing is, that she was on the phone to her mother Keira at the time, counting down the ten steps into the cellar to find the fuse box. Frustrated by the lack of leads, Keira investigates and finds that the walls have strange symbols engraved into them. After a number of terrifying supernatural experiences, she comes to the conclusion that the house took Ellie. She discovers that a physicist and occultist called John Fetherston, who was obsessed with finding the 11th dimension, built the house and engraved sinister equations on the 10 steps leading into the cellar. Finally, she must battle with the universe's most ancient evil, or lose her family's souls forever.