In the book, Ryan Perry is a dot com multi-millionaire who discovers that he has to have a heart transplant. After a year of growing panic (will he get a heart, what caused the heart problems), he flies to China to get his new heart. A year later, a strange Chinese looking woman starts sending him messages about his heart, and trying to spook him somewhat (she breaks into his house to leave "love hearts" for example). Unsurprisingly, this bugs Perry. What is bugging her about the heart and why is she so stressed anyway?
The story should be scary, could be scary, but it just isn't, and that's a big problem for a horror story.