R.J. Ellory - Simple Act of Violence

Washington, embroiled in the mid-term elections, didn't want to hear about serial killings. But when the newspapers reported a 4th murder, when they gave the killer a name and details of his horrendous crimes, there were few people who could ignore it. Detective Robert Miller is assigned to the case.
Rapidly things begin to complicate. The victims do not officially exist. Their personal details do not register on any known systems. The harder Miller works, the less it makes sense. And as Miller unearths ever more disturbing facts, he starts to face truths so far-removed from his own reality that he begins to fear for his life.