Aliens are coming to Yellowstone Global Park. In order to protect its delicate ecosystem, the park has been closed to the public for a quarter of a century. But the fortifications that keep the public away from the bison and the geysers are perfect for keeping the arriving aliens-the Stracahn-away from humanity. Solomon Brooks lives on the edge of the park, but he has never been inside. Outside the park's energy barriers, bitter land wars threaten to tear human society apart. Sol seeks refuge from the conflict by volunteering to work with the aliens inside Yellowstone. There, he meets Zyn'dri, a Stracahn girl with gifts even her own species doesn't fully understand, and Walt, a ranger whose knowledge of the park is second only to his knowledge of human nature. As the three forge an unlikely friendship, they uncover a sinister plot and realize that some humans will go to any lengths to get the aliens out. The Stracahn have come from their dying planet, Empyriad, in search of a peaceful new home. But with warring humans outside the gates of Yellowstone and the world's largest supervolcano inside, Earth is anything but peaceful.