The Laddertop space stations are an alien technology that powers the entire planet, and only a skilled crew of children can perform the maintenance necessary to keep the stations up and running. Back on Earth, competition is fierce to enter Laddertop Academy. It is an honor few students will achieve. Best friends Robbi and Azure, two 11-year-old girls, are candidates for the Academy. They will become entangled in a dangerous mystery that may help them solve the riddle of the aliens known as 'the Givers' - if it doesn't destroy the Earth first!