When a local Philadelphia radio host known for his incendiary right-wing tirades is arrested for possession of illegal prescription drugs, the incident sets into motion a series of events that leads ultimately to the death of a homeless man. In the complicated mix is the local Benedictine monastery, a Nobel-prize-winning leftist academic, and a homeless advocacy group, among others. Now Gregor Demarkian, a retired F.B.I. agent, is hired by a local...