Growing up in a remote forest cabin with his dad, Gus learns lessons about survival and the dangers that lurk beyond the fence to the outside world.

Gus and Big Man pick up a traveling companion who suggests a perilous shortcut. Aimee's sanctuary comes under threat. Time's running out for the Singhs.

Gus's quest to find Birdie and uncover more about her connection to his father leaves him questioning everything he's ever known.

After suffering an unimaginable loss, Gus must make a choice that will determine the fate of humans and hybrids. Who will be left to tell their story?