Emeryville: population 73,250, including one feared serial killer on the loose who carves the number 13 into his victims' chests. Sara is home alone on a stormy night when there is a knock at the door. Andrew, a real estate consultant, has stopped by regarding the sale of her house. Problem is, the house isn't for sale. Against her better judgment, she grants Andrew shelter from the rain. But tension builds as Andrew, talking about his impending custody battle for his daughter, becomes more and more agitated. Sara finds herself in possible peril, until there is another knock at the door. John, a scripture-quoting home security technician, has stopped by to fix a fuse. But he may not be all he seems when a knife is found in his bag. Cautious cat-and-mouse play ensues as the trio tries to determine just who the true threat is, while a surprise twist leaves you wondering just who it is that really needs to be saved ...