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 follows a reluctant Big Man into the unknown. Dr. Singh discovers what it will cost to save Rani. Aimee finds a new beginning after the world ends.

His world shaken, Gus runs off and makes a rash decision. Big Man comes to grips with long-ago mistakes. Aimee makes a last stand against General Abbot.

Locked up in the zoo's kennels, Gus meets his fellow hybrid prisoners as he looks for a way out. General Abbot pressures Dr. Singh to produce a cure.

Warned about General Abbot's plans, Gus and his friends prepare to take a stand and defend the hybrid kids, no matter what it takes.