In a world where mythical creatures are real, yet unseen by us normal folks, Finn runs The Au Fae Detective Agency. With Bob, the sarcastic Bobcat, along with the help of Ami, a Fae police officer, they get caught in a fresh case that isn't as simple as it first seems. A historic knife, the Sgian Salann, is stolen from a prominent Nymph family, and Finn and the team are tasked with finding it. This leads them through the seedy underworld of the Fae and As Sidhe, with Goblins, Brownies and, of course, Kelpies, the ancient enemy of the Nymphs who may no longer be as dormant as they once appeared...