London, 1383. William the weaver bursts into Brother Athelstan’s church, desperately seeking sanctuary. His crime? The bloody murder of a vicious loan shark. Athelstan takes him in, but a short while later William lies dead in the locked church. Who would take revenge for the death of a universally hated man – and how did they commit an almost impossible crime?

Athelstan’s investigations are complicated by news of the murder of an eminent member of the Guild of Fishmongers, an ominous message left on his corpse. More deaths quickly follow. Athelstan and his old friend, the coroner Sir John Cranston, realise they have a serial killer on their hands.

But when their investigations lead to the small priory of St Osyth’s, which hides a shocking secret, Athelstan starts to realise there’s much more at stake than catching a twisted killer – and the truth will shock even as experienced a sleuth as him . . .