In an American desert town circa 1955, the itinerary of a Junior Stargazer/Space Cadet convention is spectacularly disrupted by world-changing events.

Blue Peter presenters Helen Skelton and Barney Harwood want to learn more about the solar system so they challenge scientists Helen Czerski and Jem Stansfield to find out more. They look at how to make telescopes and rockets, and use a toilet roll to measure the distances between planets.