An original science fiction tale by the bestselling author of Ender’s Game and his daughterTwenty-five years ago, the alien Givers came to Earth and bestowed upon the human race the greatest technology ever seen—four 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 ...