Publisher's Synopsis
Twenty-five years ago, the alien Givers came to Earth and bestowed upon the human race the greatest technology ever seenfour giant towers known as Ladders that rise thirty-six thousand miles and culminate in space stations that power the entire planet. Then, for reasons unknown, the Givers disappeared. Due to the unique alien construction of the Laddertop space stations, only a skilled crew of children can perform the maintenance necessary to keep the stations up and running.
