Dr. Sara Linton has seen some gruesome sights in her work, but nothing has prepared her for the woman brought into the ER after being hit by a car. Sara's exam reveals that the woman had been bound, starved and tortured before the accident. Georgia Bureau of Investigation agents Will Trent and Faith Mitchell happen to be at the hospital when the patient is brought in, and they immediately become involved, with the grudging assistance of the local cops. When Will goes out to investigate at the accident scene, he finds another victim (later identified as Jacqueline "Jackie" Zabel) and an underground torture chamber. Jackie is dead; they later discover that she committed suicide. Apparently, the two women had escaped their captor and Jackie had killed herself rather than risk being recaptured.

As Sara strives to save the life of the surviving victim, known only as "Anna," Will and Faith piece together clues about Jackie's life and try to determine what the two women may have had in common. With Anna virtually comatose, the two agents have no witnesses and little trace evidence from the underground chamber. But the items they find there and the injuries that Anna and Jackie sustained are horrifying, even to the experienced GBI agents. When a woman disappears from a grocery store parking lot, leaving behind her young son, Will and Faith find disturbing similarities between her life, Anna's and Jackie's. The investigation becomes a race against time to save the latest victim.

This story brings back some familiar characters from previous books: Sara, Will and Faith. They are all dealing with personal issues of their own -- Sara with the death of her husband, Will with his troubled past, and Faith with two serious health issues. These struggles make them compelling characters who are vulnerable yet driven, personally and professionally. I found myself as interested in the personal lives of the investigators as I was in how they were solving the case. One intriguing twist is that the victims are not very likable people, despite what they have been through, which creates a conflict for the reader.

Don't start this book at night, because once you begin, you won't want to put it down! And when you're done, you'll probably want to sleep with the lights on...