For three generations, the Deep-Kin were a story — an exile clan that the Compact had sealed underground and forgotten. Scout-Second Valla Stone-Path believed the story, until the night the story climbed out of the stone and destroyed everything she knew.

Deep-Ridge Outpost falls in an hour. Sixty soldiers die. Eleven survivors escape through a maintenance shaft, carrying nothing but the clothes on their backs and a relay engineer who might be able to send a warning through a communication network that's been rotting from neglect.

A hundred miles of frozen mountain passes lie between them and Iron-Hold. The terrain is hostile, the weather is lethal, and the Deep-Kin are tracking them through the stone itself. Valla's only assets are a tunnel fighter who's afraid of heights, a medic with a dark past, a young engineer who still believes in the system that failed them, and a group of survivors who've never had to run for their lives.

But the hardest part of the march isn't the terrain. It's the decisions. Who gets medicine. Who walks. Who fights. Who lives.