Someone is murdering unfaithful men and dismembering their bodies. To get to victims, the killer uses "alibi services," companies that provide alibis to people who are having an affair. Special Agent Mary Stevens works in the Investigative Support Unit at the FBI, a unit that handles serial crimes, including those of serial killers. Can she stop the Alibi Murderer, when she doesn't even know whether it's a man or a woman? This tautly written thriller features a strong and singular heroine and a wily and focused killer, both bent on carrying out their own definition of "justice."