In this new installment of the popular, puzzle-based series, Kate has settled into her new life running the Avondale Puzzle Museum in Granville, New Hampshire. The locals have begun to accept her presence - until a serial killer from Boston starts making his way north up I-93. At the same time a former partner of Police Chief Brandon"s shows up with information about the killer who has just struck Granville and put the Police Chief out of commission. The same killer who leaves a puzzle at each crime scene, and is now focused on Kate.