When a robot dog from the future pops up in their backyard on a mission to help them, 11-year-old James and his beloved golden retriever, Rex, learn that it is up to them to save the world from Dr. Apocalypse, an evil scientist, and his wily robotic Destructo-Cat.

America is in the midst of the Great Depression, and the Kamp family is struggling to get by, especially since Mrs. Kamp’s untimely death nearly a year ago. The older children do their best to take care of the family, but it’s the younger children—Hopalong Cassidy fan Norman and straight-talking little Ruthie—who struggle most. Now, with their mother gone and their father overwhelmed by doctor bills from young Norman’s battle with polio, the Kamp siblings fully expect a Christmas without presents. But when William scrapes together a dollar in coins to use for Christmas gifts, everything begins to change.