June, 1381. The rebel armies are massed outside London, determined to overturn both Crown and Church. The Regent, John of Gaunt, has headed north, leaving his nephew, the boy-king Richard II, unprotected.

Brother Athelstan meanwhile has been summoned to the monastery at Blackfriars, tasked with solving the murder of his fellow priest, Brother Alberic, found stabbed to death in his locked chamber. Athelstan would rather be protecting his parishioners at St Erconwald's. Instead, he finds himself investigating a royal murder that took place fifty-four years earlier whilst the rebel leaders plot the present king's destruction.

What does the fate of the king's great-grandfather, Edward II, have to do with the murder of Brother Alberic more than fifty years later? When he finds his own life under threat, Athelstan discovers that exposing past secrets can lead to present danger.