A profiler. A physical therapist. A killer who leaves little trace.

When FBI Behavioral Analysis Unit Coordinator John Martin is assigned to a string of brutal murders in San Francisco, he expects resistance from local law enforcement?not from a civilian witness. But Katelyn Harris isn't just any witness. She's a physical therapist with an expert understanding of human movement?first brought into the case as an expert witness, she soon becomes a target of an attack by the very killer John is hunting, barely escaping.
Katelyn insists she can identify her attacker by his gait?the subtle irregularities in his stride no one else would notice. The police are skeptical. The evidence is thin. And the killer is still stalking his next victim.
As professional tension between John and Katelyn ignites into something far more complicated, a shadowy figure known only as the "Chronicler" begins documenting every gruesome detail of the crimes. Is the Chronicler the murderer... or someone even closer to the case?
With time running out and no physical evidence to rely on, John and Katelyn must trust each other to stop a predator who has already chosen his next target.

And he's not finished yet.