The show primarily follows the lives of three orphaned children called Mel, Josh, and Lucy Barker, and their new foster parents Brian and Sophie Johnson.

[1] The children soon discover that the Johnsons are in fact aliens from the planet Valux, who crash-landed on Earth when Brian tampered with the controls of their spaceship.

Whilst being a children's show, it occasionally makes reference to rather mature matters, high-brow culture, and complex scientific thinking; and because of this, it has also gained a considerable following of older viewers outside of its intended age range.

The new plot acted as a clean slate for the show, with Brian and Sophie crashing their ship again and taking in a new family of foster children after having their memories of the past seven years erased by Guido, the new avatar of the galactic guidebook.

However the new status quo was not to last long, as in 2006, it was announced by ITV that they were to close its in-house children's production unit, bringing the show to a sudden end following series 8.