Forensic Pathologist Dr. Samantha Ryan moves back to Cambridge from London to take up a consultant's post at the Park Teaching Hospital. Sam's first case is the tragic death of a six-year-old girl, Sarah Crew, who is thought to have fallen from a rope swing over a river and drowned. But when Sam finds evidence of previous physical abuse, Inspector Tom Adams begins a murder investigation.

Dr. Sam Ryan is called to the scene of the murder of Mark James, a young man whose badly decomposed body cannot hide the signs of a ritual element to the killing: there is an upside-down cross scored on his back and a ligature around his neck. Then when a second murder follows, Sam follows the trail of clues into the world of the occult.

When a death occurs in police custody, the footprints of the man who was sharing his cell are found all over the body. It looks like an open and shut case for Dr. Sam Ryan. But just as the investigation appears to be over, Sam receives a note written on police notepaper that re-opens the case. It seems that the real culprit may have been a police officer, but which one?

Sam is called to the scene of a restaurant fire where DI Adams needs her help to identify a badly burnt body. It emerges that the prime suspect is one of Sam's students, who had come to her for advice recently, and Sam needs to decide whether to tell the police. Then when further tragedy strikes, both Sam and DI Adams must face up to their own demons and secrets.