In case you didn't pick it up from the title, CS Sansom's book is based in that period in English history when King Henry VIII went about closing the monasteries (1536 - 1540). Cromwell, Henry VIII's Vicar General sent out his agents to gather "the dirt" on all the abbeys and monasteries throughout England - he wanted to know about their wealth, their vices, and their adherence to the "new faith".
So enters one Matthew Shardlake, lawyer and support of the "reformists", sent out by Cromwell to investigate the murder of one of his Commissioners at a remote Sussex monastery.
And so the story continues ..... and what begins as a murder investigation soon develops into a questioning of faith and religion.
Without giving too much away, the plots twist and turn, culminating in a link back to Anne Bolyen, second wife of Henry VIII, who encouraged Henry to abandon the Papacy and become Supreme Head of the Church in England.
It is an interesting look into that period in English history where the new "reformist" religion was taking shape under Henry VIII - and to what extent adherence was enforced.