Ten thousand years ago, a vast, fertile plain linked the British Isles to Europe. Home to a tribe of simple hunter-gatherers, Northland teems with nature's bounty, but is also subject to its whims. Fourteen-year-old Ana calls Northland home, but her world is changing. The air is warming, the ice is melting, and the seas are rising. One day Ana meets a traveler from a far-distant city called Jericho- a town that is protected by a wall. And she starts to imagine the impossible... So begins a colossal engineering project that will take decades: the building of a wall that stretches for hundreds of miles- a wall that becomes an act of defiance against the implacable forces of nature, and an act of devotion as the bones of the dead are added to it. A wall that will change the geography of the world. And its history.