When George a Becky are playing in the attic, they come across a secret room that belonged to a boy named Russell when he lived in the house 70 years ago. They find a journal detailing how Russell's favourite toy, Space Boy Bob, went missing in the backyard pond. George sets out in his Zoopersub to find the toy as well as plenty of adventure down under. After a close encounter with the pond's villain, a turtle named Snapper, George recovers the missing toys and returns them to a very appreciative and now 80 year old Russell.