King Henry VIII is wooing Lady Catherine Parr, whom he wants for his sixth wife. But this time the object of his affections is resisting. Archbishop Cranmer and the embattled Protestant faction at court are watching keenly, for Lady Catherine is known to share their reformist sympathies.

Matthew Shardlake, meanwhile, is working on the case of a teenage boy, a religious maniac who has been placed by the King's council in the Bedlam hospital for the insane. Should he be released as his parents want, when his terrifying actions could lead to him being burned as a heretic?

When an old friend is horrifically murdered, Shardlake promises his widow, for whom he has long had complicated feelings, to bring the killer to justice. His search leads him to connections not only with the boy in Bedlam but with Cranmer and Catherine Parr and with the dark prophecies of the Book of Revelation.

As London's Bishop Bonner prepares a purge of Protestants, Shardlake, together with his assistant Jack Barak and his friend Guy Malton, follows the trail of a series of horrific murders that shake them all to the core, and which are already igniting frenzied talk of witchcraft and demonic possession. For what else would the Tudor mind make of a serial killer...?