A strange black orb appears. First Toronto. Then New York. Then Beijing. And then people start disappearing. Sixteen-year-old Kris watches her mother vanish as the first orb hovers over a downtown square. More follow. Entire cities empty. The world is running out of time. Kris is an exceptional young mind, so she sees what others miss: the flashing patterns in the orbs aren't random. They're mathematical. When a team of the world's brightest scientists confirms she's right, the race to decode the message falls to her. Each breakthrough pulls her deeper, and the patterns from the sky call to her. With her older sister's help, Kris chases clues that could return the taken. But the more she understands, the clearer it becomes that the next step is hers alone.