Following an assault, Emma Webster spends two years as a self-sentenced prisoner locked inside her condo, living a lonely but safe existence - at least she thought it was safe until the world outside her window goes still and silent.

Troy Nanson, a bicycle messenger, awakens in a hospital with no memory of how she got there or how long she lay unconscious. When her calls for help go unanswered, Troy dials 911, but no one answers. As Troy explores a silent city, her suspicions are confirmed - the rest of the world has fallen asleep, and nothing she does will wake them. Fear and desperation cause Troy's tenuous grip on reality to slip. She's ready to give up, until then she finds Emma.

Believing they are the only people awake in the entire world, two women who are as different from each other as they could possibly be, come to depend on one another for safety and sanity—and eventually, much more.