​Revenge is a promise he made in the dark, and he intends to keep it, even if it burns the entire world above down. After losing his sister to the hunters above, he has spent years becoming the very thing they will fear. ​He spent years decoding the secrets of the surface, meticulously plotting a path of vengeance. Now he was ready​, the only complication is Sadie. She believes in his lies, and she trusts the man he pretends to be. He swore he would stop for her, but the pull of the past is stronger than the hope of a future. As the clock ticks toward his final, devastating move, he stands on the edge of a catastrophe he can no longer control. Will his vengeance finally be served, or will his own path of ruin claim the one person he was supposed to save?