Spring 1261. In Rome, Pope Alexander lies dying. Across Europe, in Oxford's Oseney Abbey, ambitious Bishop Otho is already positioning himself as successor. Almost immediately, a student protest against the greed of the Church spirals out of control and the bishop's brother is killed. Everyone assumes the fatal arrow was meant for the bishop himself, and the protesters are swiftly accused of murder and imprisoned in an Oxford gaol. But with no motive, William Falconer can't believe his students would do such a thing. And when the prime suspect is found hanging in his cell the next day, Falconer knows there's more to this than a case of mistaken identity. With his trusted friend, and town constable, Peter Bullock, Falconer must use his famed logic to solve a murderous riddle. Who is the real killer? And who is the real target?