Kendra Blake doesn't much feel like celebrating these days. Her eighteenth birthday should be a happy time, but all she can think about is her brother, Harris, and how he disappeared five years ago. And he wasn't the only one-across the world, there's been an alarming rise in disappearances of eighteen-year-olds. When Kendra goes back to school, approached by Richmond Gideon, billionaire owner of the space company Minerva, she figures out why.

To combat climate change and overpopulation, all eighteen-year-olds must pass a series of coming-of-age tests on a desert planet called Astrid to prove they're worthy to live on Earth. Those who fail the ritual are abandoned on the planet while those who pass return home to have their memories erased. And Kendra's brother, Harris, was one of them-and now, she will be, too.

With no other choice, Kendra goes with Gideon to Astrid where she encounters human-like aliens, some with a grudge for invading their planet. With the help of local native, Kai, who she eventually develops feelings for, she just might have a chance of surviving and getting home-but the test isn't as easy as she thinks. With a brother to find, tests to pass, and a rebellion to lead, Kendra must fight for a better future for Earth and Astrid-before it's taken forever.