For those who enjoyed Umberto Eco's The Name of the Rose, Sarah Perry's The Essex Serpent and Chris Carter's The X-Files, Dan Jones has distilled a monastic detective adventure that goes back to the late medieval period in which he specialises. We are in Northern Italy in 1367, in the company of the esteemed scholar and Holy Inquisitor Brother Jacobus of Vienna, who has made a habit of intervening in inquisitorial trials, using reason to test religious superstition and speculation. Sent to examine a new case, Jacobus applies the sound principles of rigorous research and philosophical logic, and manages to acquit an innocent woman tried for sorcery, much to the irritation of the cardinals at the Papal Palace in Avignon, who thereby feel defied.

When Jacobus hears of a mysterious spate of infant disappearances in a remote community in Northern England, his intellectual curiosity is again piqued and he takes off to solve the mystery, once again in defiance of the cardinals. Arriving in England, he finds a land that's in a state of dissarray, beset by Scottish raiders, litigious noblemen, eccentric Franciscan friars- and talk of demons in the woods. All the while, spectres of violence, both ancient and new, lurk behind every stone and tree.

Jacobus is determined to discover the cause of the disappearances, but is waylaid by something monstrous in the forest that neither his science nor his faith can explain. As he struggles to solve this very different puzzle from the one that brought him to England, his deceptions catch up with him, and he faces a terrible crisis that will either destroy his philosophical beliefs or shatter his soul.