Nix is fourteen years old, blue-skinned and storm-haired, and his magic has just torn through him in the middle of a winter forest, eight years before it was ever meant to arrive. It left a wound in his chest and something dangerous loose in the world, and now he is running. Three brothers find him bleeding in the Sentinel Forest and do not turn away. What follows is their journey together through MirMarnia, an ancient world of breathing forests, river magic, and creatures older than any name for them, as four unlikely companions discover that the things hunting Nix are only the beginning of what this world has in store.