In 1539 King Henry VIII is completing his ruthless destruction of England's monasteries. And the ripples of this seismic change are felt even in the small northern port of Liverpool.

When novice nun, Agnes Moore, ejected from her convent and staying with resentful relatives, claims to have been attacked in the ancient chapel of St Mary del Quay on Liverpool's waterfront by Satan himself, her former abbess, Lady Katheryn Bulkeley, comes to her aid. Then a young priest is found dead in the River Mersey, his right hand hacked off, and Katheryn suspects that Liverpool harbours some disturbing secrets.

The pregnant Agnes refuses to reveal her lover's identity and when she is brutally murdered, Katheryn must seek her killer amongst Liverpool's highest and lowest citizens. Then corpses are mutilated in a local churchyard and it seems that this evil may be linked to Agnes's death.

As Katheryn uncovers more of Liverpool's dark side and draws closer to the truth, she must find the answer to the most urgent questions of all. Why has such evil come to the town? And who is the devil's priest?