When Matt Ballard was starting out his career, three boys were murdered in the same area, the remote and bleak Gibbet Fen. When the main suspect was killed in a hit-and-run, the killings stopped. But Matt was not satisfied that the real murderer had been caught. Over 25 years later, Matt gets a photo in an unmarked envelope. It's of the Gibbet Fen crime scene. And the picture was taken before the murder took place. More photos arrive, relating to the historic murders, as well as intimate pictures of Matt's very secret private life.

Grace Repton, a beautiful older woman, walks into the police station to tell Detective Matt Ballard she has information that could stop a murder. Her fiance, the infamous serial killer Jeremy Reader, has told her that he has a disciple who is going to kill using Reader's horrific methods. Reader murdered five women and was finally brought to justice by Detective Ballard. Reader is safely imprisoned in a high security prison, and claiming to be a reformed man who wants to help the police.   

As the mists roll over the fens and enigmatic lights twinkle in the distance, only the locals know their way along the hidden paths through the mysterious watery terrain of one of England's most beautiful and sometimes dangerous places. Detective Matt Ballard may have retired but there's still plenty going on in the fens to keep him busy. Someone trashes an old lady's garden and daubs her isolated cottage with hateful graffiti. Emilia Swain seems to be totally harmless, so why is she being targeted?