A foot in a geyser. A school in the wild. A truth no one saw coming.

When a human foot is ejected from a geyser in Yellowstone National Park, Special Agent Emme Helliwell of the National Park Service is assigned the chilling case.

Tasked with identifying the victim and uncovering what led to such a grisly end, Emme is drawn into the park's vast, unforgiving wilderness—and into the orbit of a private school for at-risk teens where extreme backcountry excursions are part of the curriculum. As disturbing truths begin to surface, Emme must also confront personal fault lines, including the unresolved tension with an ex-boyfriend who's suddenly back in her life and assigned to the same case.

In a place where danger hides behind natural beauty and good intentions can mask darker motives, Emme must navigate both treacherous terrain and emotional landmines to solve a mystery that could cost her everything.