Ishek clings to existence in the depths of the forest, surrounded by unstoppable creatures that patrol its borders. Hast and his family are elected for the hunt, a dangerous foray into the territory of the monsters. Days into the incursion, Hast's party is ambushed and destroyed by a ravenous hartak pack, but in the medley, Hast lost sight of his brother. Helpless and lost in an unforgiving forest, Hast has no choice but to rely on the very creature that killed his family to shepherd him home and to be reunited with his brother, if he survived. Together they stumble upon the deadly corruption that is black moss, and are bound together by its sickly threads. Their minds now connected, Hast must tame his companion's viscous appetite while feeding the moss that still worms its way through his body, or else become prey to both.