After her mother dies, 17-year-old Mary Katherine, or M.K., moves in with her eccentric scientist father Professor Bomba, who has spent his life searching for tiny humanoid soldiers called Leafmen in Danbury, Connecticut. They protect the forest near where Bomba lives from wicked creatures called Boggans and their malevolent leader Mandrake. Bomba’s determination to find proof of his theories irritates his daughter as she believes it’s nonsense, like her mother did, but Bomba assures her he’ll find proof.