Twenty-five years into the future, no humans are allowed in the Wildlands - a vast area in Britain where wolves, lynx and bison roam free. The only exception is a high-speed train line between London and Glasgow that crosses right through the heart of the project.

Thirteen-year-old Astrid and her little sister, Indie, are onboard when their train slows to a brief, unexpected stop ... and they find themselves accidentally left behind.

Stranded in this place of astonishing natural wonders and terrible dangers, they have only a rucksack, a phone without signal - and each other. As every wrong turn takes them deeper into the Wildlands, do they have the ingenuity and determination to survive?

How far would YOU go to find your way home?