Mark Stafford is a sketch artist for the Philadelphia Police Department; who suffers from split personality disorder. His other personality, whom he is completely unaware of, is a serial killer. The killer's targets are the men that Mark sketches. The novel jumps between the point of view of the two personalities that both lead very separate lives; until one day Mark notices some irregularities in the number of arrests his sketches have led to, and the number of dead or missing suspects he has is getting higher by the case. As Mark recruits the help of his friend and co-worker, Detective Pierce Noland, he is forced to reconcile his mysterious past in order to find the true identity of the killer.