When a mysterious message from the stars threatens the solar system, Quelly Clary’s geology expertise may offer the best hope to solve a billion-year-old interplanetary mystery, but only if she can overcome past betrayal and team up with the rich and arrogant "Barn" McAdams.

Quelly, a prickly high school dropout and self-taught planetary processes expert, takes one of the luxury Loop Ships out to Callisto, determined to avenge a murder and locate an alien artifact, but begins to wonder if her own team might pose the greatest danger. Teaming up with Barn McAdams, a wealthy ne'er-do-well who keeps giving her his unwanted advice, proves particularly challenging. But the fate of humanity and any understanding of the deadly threat from the stars may depend on her courage to trust her team, as well as on her skills in scientific deduction and her ability to survive the assassins hiding among her colleagues on the ship.

This story is appropriate for ages 14 and up.