Priest and trainee exorcist Merrily Watkins is asked for help by police in solving a baffling and gruesome murder. She quickly becomes embroiled in a terrifying mystery and finds herself in real danger.

Merrily is on a quest for answers after a murder, a desecrated church and a clergyman's apparent `suicide'. She suspects a Satanic group may be at work, and is guided through a ceremony of lesser exorcism by Huw Owen, but nothing can prepare her for what she is about to uncover.