Becket, walking her dog one winter evening, fears it's an abandoned baby left out in the cold. But it is something else - something evil - and it tricks Becket into opening a doorway to another realm, letting a darkness into our world, a corruption that begins transforming Philadelphia into a sinister and menacing version of itself...but only at night. The changes are subtle are first, causing Becket to doubt her senses and her sanity. But soon the nightmarish truth is impossible to deny: By day, the city is just a city, but at night it literally comes alive with malevolent purpose. Brick and steel become bone, streetlights turn into gallows, and hungry alleys wait to snare mortal victims. Terrified citizens huddle indoors after dusk, even as others succumb to the siren song of the night, letting their darker sides run wild. Once, Becket's biggest problems were living up to her police commissioner father's high expectations and enduring a secret crush on her best friend's boyfriend. Now she must find a way to survive and protect her loved ones...before the darkness takes her as well.