How do you stop a killer you can't even see?

It's been two years since Detective Marissa Ambrose nearly lost her life working the Couple’s Killer case, but time hasn't stopped the vivid nightmares. She still carries the heavy guilt of her partner's death, and the Seattle Police Department refuses to support her theory that the suspect they arrested had an accomplice. With her ex-husband regretfully out of the picture, Marissa was supposed to be focusing on adjusting back to something resembling normalcy in her quiet tourist town. Then the letters came.

Unmarked envelopes full of photographs have been arriving at Marissa's door. Candid shots of her at home. Now, Marissa is certain the missing murderer is stalking her, tracking her every move to finish what he started. As she obsesses over the strange images, the Seattle PD unexpectedly asks for her help. A serial killer is on the loose and targeting members of the Port Townsend community. Despite a personal connection to the first victim, Marissa agrees to pin her badge on once more.

The photographs are piling up and the suspect can't be seen by surveillance cameras. Like a ghost, this killer is haunting her.