Four childhood friends from different backgrounds (Reniel, Bartholomew, Bobson, and Ceonred) all receive a letter from one of their childhood gang of ragamuffins: Calli, telling them all she has uncovered a dangerous secret through her time in academia and is being hunted for it, and is in hiding in the forbidden, cursed fortress of Blackhall.
The group's paths have wildly diverged. An encounter with cultists led to the death of Ceonred's beloved older brother, and caused the group to splinter apart; Cei joined the Church of Aeo, becoming a feared Purifier General. She joins the group accompanied by a man-at-arms, also of the Church (Horace).
They delve into the depths of Blackhall-- the final stronghold of the great historical traitor, Charl-- and find two prisoners, being tortured by demon cultists to an unknown end. They free them. Lyra (a hunter with unusual abilities) and Cyrus (a mage of the Circle of Thorns) decide to accompany them for the time being.
They discover several terrible truths in Blackhall. It turns out their old friend Calli had laid a trap for them and had fallen into trafficking with demonic powers; they are forced to slay her to defend themselves. For another, they discover that one of the commanders of the victorious army-- Purifier-General Ysemir Hastingmoor-- confessed in his suicide note that the great historical traitor Charl was in fact a blameless hero who had been betrayed, and falsely slandered by history. They manage to lay the ghosts of the past to rest, and the dark and cursed miasma that hangs about Blackhall dissipates.
They return to the city. Cei is grappling with learning that the dogma upon which her faith rests is in part founded on lies. They decide to lay low for a few days, and hole up at an inn on the outskirts of the city. Cei sequesters herself for three days of fasting and prayer; after three days, a messenger arrives with a message from her Church masters. They bid her to investigate an accusation of witchcraft in the eastern town of Anger's Edge.
They quickly discover that the accused (a girl named Loredana) is innocent, despite having some unusual powers. They arrange to have her (and her new friend, a thief named Selene who the party accosted earlier) to escape to seek the protection of the Circle of Thorns. They discover enormous corruption at work in the town and its governance, all culminating in Lord Asher, the town and the surrounding area's ruler. They decide to discreetly investigate his manor house. Bartholomew seeks entry as a wandering minstrel and is unfortunately immediately recognized and accosted by Lord Asher, his unsettling sister, an assassin who the group had earlier been waylaid by, and their hired thugs. In the sewers under the manor house, Lyra finds evidence of truly vile slaughter and murder of what appears to be many young innocents. The party decides they must intervene immediately, and Cei compels the guardsfolk to stand aside or be struck down by Aeo's inquisition.
A fierce battle ensues...