Nelly Rapp has to go with mom and dad to dinner with uncle Hannibal, an odd figure they hadn’t heard from for a long time before he suddenly reconnected, saying he wants to meet his little relative, Nelly. But there is something mysterious about uncle Hannibal, and when his butler lures Nelly and her dog London into the attic, she begins to get scared. Nelly’s nerves get even more frazzled when the lights suddenly go out and a hand pulls her into a room. The hand turns out to belong to Lena-Sleva, a teacher at the Monster Academy, who is eagerly awaiting her tenth student.

Nelly and her dog London are soon embroiled into an adventure where they come face to face with a bloodthirsty vampire – one who has a toothache, to boot! This is just one of the many tests she must pass in order to be admitted to the Monster Academy, the school that trains monster agents! Nelly learns to identify and fight scary creatures, without falling victim to her fear. As a full-fledged agent, she and London deceive the entire world of ghosts and monsters by using the three C’s: calmness, cleverness and cunning.