Demons are very real; once every hundred years when the right conditions are met, a sin can step foot on Earth. Zack learned this the hard way when he accidentally crossed paths with a sin on his way home from a party, and now he is cursed to be a vessel. He thought freshmen year at the University of Waterloo was already enough pressure, now he has to avoid exorcists and unravel the mystery of who the sin is if he ever wants to be human again.