Whispers by Dean Koontz

A successful actress finds her life invaded by a relentless, sexually obsessed stranger whose stalking escalates into savage violence and irrational threats; when a reclusive man is pulled into protecting her, they begin to unravel the killer’s disturbing past and hidden connections, leading to tense investigations, shocking revelations, and a violent confrontation that probes the limits of obsession, identity, and human cruelty.