Kieran runs the only diner in the Land of Monsters-and he's really good at it. But when the head zookeeper asks him to catch an escaped water sprite in the human world, his quiet life gets anything but quiet. With his best friend Lysander and his two dads by his side, Kieran heads to Butterfly Lake for what should be a simple rescue mission. Except nothing turns out the way he expects, and Kieran will have to decide what's more important: following orders or doing what's right.