Archibald, a shy and observant boy, has a dream: to become a great detective. And not just any sort of detective! He wants to explore secret worlds, those where magic reigns and monsters lurk in the shadows. All he needs is his first big case! When it arrives in the form of Monk, a talkative and cowardly, one-eyed dog, Archibald is introduced to the Monster Investigation Bureau.

Together, Archibald and Monk set out on the trail of a giant snake, a mysterious black mage, and an army of zombies...and along the way, encounter a war declared between the werewolves and the bear-men, and a horde of goblins who harass trolls, among other curious creatures. Thrills, chills, humor, blunders, and more are in store for the adventures of this unique tandem of Sherlock Holmes apprentices!