Out of deep space, a mysterious alien race known as "The Givers" came to Earth. They gave the human race the greatest technology ever seen—four giant towers known as Ladders that rose 36,000 miles into space. Each tower culminated in a space station that harnessed the energy of the Sun to power the entire planet. As suddenly as the Givers arrived, they vanished, leaving the human race with one solemn instruction: maintain and preserve the Ladders at all costs. Due to the unique alien construction of the Laddertop space stations, however, only a skilled crew of children could perform the maintenance necessary to keep the stations running. Twenty-five years later, back on Earth, competition is fierce to enter Laddertop Academy. Robbi and Azure, two eleven-year-old girls who are best friends, are among those vying for a spot at the prestigious academy. While one is rejected, the other takes off into space for the adventure of a lifetime. Yet soon, their destinies will collide, as they must decipher an alien message and solve an ancient mystery that could either save the Earth from invasion...or trigger its imminent destruction.