After a traumatic experience steals her younger sister Guthrie's voice, sixteen-year-old Chase and her family move to an isolated fire lookout in Pando, a grove of Aspen tree clones connected by a massive underground root system. The lookout is supposed to give the family stability after years spent traveling the country in a converted school bus, but all Chase wants is to go back to the hometown they fled eight years ago. When Chase gets a job at a nearby summer camp, she learns that something happened at the lookout, something no one wants to talk about. Chase isn't entirely surprised: Pando is a place where odd things happen, like birds singing on a loop or bones sprouting out of the ground like wildflowers. Worse? Pando is changing Guthrie, and Chase doesn't know how to stop it or even if she should. Despite her resolve to protect Guthrie, Chase becomes increasingly distracted by Wilder, the lifeguard at camp who offers her a taste of normalcy and a new perspective on her skoolie family. But more time with Wilder means less time with Guthrie, and the mysterious force in the forest draws Guthrie deeper into its darkness--until she's nowhere to be found. Chase must face her own childhood trauma and find her way into a strange and sinister world to rescue her sister before Guthrie is lost to the lonely places forever.