Nemo is a young boy who has a vivid imagination. He is also somewhat of a troublemaker, although he means no harm, by constantly breaking his promises not to steal his mother's baked goods late at night. One night, Nemo is convinced to travel to Slumberland by Professor Genius, King Morpheus' royal assistant, and is taken by dirigible to Slumberland to be Princess Camille's official playmate. Once there, King Morpheus announces that Nemo is to be heir of the Slumberland throne, and gives Nemo a special key that can open any door. Morpheus warns Nemo not to open the door with the large symbol on it. Through Flip, a wanted criminal, Nemo's curiosity gets the better of him, and he unlocks the forbidden door, unleashing all sorts of nightmares unto the innocent Slumberland, and causing King Morpheus to be kidnapped. With the power of his new friends, and the Royal Scepter, Nemo must travel to Nightmare Land to defeat the Nightmare King and undo his mistakes, before everyone's good dreams are lost forever.