The Mile Marker Murders #694349

When Caleb Williamson, a career officer with the CIA, disappears, officials are left wondering whether he is a spy who has defected or the victim of a crime.

Meanwhile, Williamson's friend, FBI agent Tyler Bannister, is focused on catching an extortionist who has threatened to unleash a biological poison if a multimillion dollar demand is not met. When Williamson turns up dead alongside the corpses of two women near a northern Virginia highway, Bannister is assigned to a task force to identify what looks to be a cunning serial killer. While Bannister becomes obsessed with finding the murderer before he strikes again, a fourth body is discovered.

The stakes become more personal when the killer targets Bannister's new love interest.