Auggie loves his job at the Fabled Stables, but he fears the day when it will come to an end. Fen keeps dropping hints that caretakers don't stay forever, and it's giving Auggie the grumps. Thankfully, there always seems to be a new stall to fill. This time, the stables set Auggie on a quest to rescue a beast called the Shibboleth--but the portal leads Auggie and Fen to the lair of the evil Rooks!

In the dark, damp dungeon, they meet one mysterious girl and one very hungry monster. It's already gobbled up all of the Rooks, and Auggie and Fen are next unless they figure out the one way to calm the creature. Will they be able to work together to complete the mission before it's too late?