Out in the Dust, humanity is at war with the sabbers, a race of brutal, wolf-like warriors. Inside Crath City, humanity is at war with the past. At the center of the city is a mysterious library containing the complete knowledge of ages before the Dust, when humanity could cure disease and reach into the stars. For Livira's people, this library holds the potential for salvation -- if only the right books can be found amidst the endless shelves.

For Evar and his four adopted siblings, the library is both a prison and a sanctuary. After being sucked out of their own times by the Mechanism, a device that lets people enter the world of whatever book they are carrying, they have been raised in inescapable isolation within the library by the dispassionate Assistant and protected from the dangers of the Mechanism by the lethal Soldier.