When a mysterious plague breaks out in the army fort guarding Vilnoc, the port capital of the duchy of Orbas, Temple sorcerer Penric and his demon Desdemona are called upon by General Arisaydia to resurrect Penric's medical skills and solve its lethal riddle. In the grueling days that follow, Pen will find that even his magic is not enough to meet the challenges without help from dedicated new colleagues—and the god of mischance.