Ramon Ridley finishes rejuvenating Old Earth and swears the Valiant crew to secrecy. He gives them a homing device that will attract the Dogstar and to everyone's surprise, it works! The crew return to New Earth with the Dogstar but are greeted by mass panic. Bob Santino has accidentally sent Robogs digging to the core of New Earth where they have triggered earthquakes. New Earth is about to implode. It's time to leave. But where to? The kids have to break their promise to Ramon but in return extract a promise from everyone to look after their old planet. Everyone is reunited with their pet dogs on Old Earth. But will history repeat itself? Probably, if human nature is anything to go by.