Ten-year-old Sam Middleton has just moved (against his wishes) to the musty old house in a New England college town where his artsy parents intend to open a gallery. Lying in the dark of his new bedroom, he hears a strange scratching and discovers a tiny, middle-aged man in a mouse suit. Jolly Goodfellow, the chief chronicler of The Sacred Seal, is a fairy-like "Sage"--"that 'little voice' of inspiration" that helps gifted humans achieve greatness. The proverb-spouting Mr. Goodfellow, whose "assignments" have included Albert Einstein, wants to find an eccentric ancient-history professor who has mysteriously disappeared, along with a legendary scroll. Sam soon finds himself fending off "Fen" (demonic muses who corrupt the good works of the Sage), as well as the suspicious Professor Mandrake and his sadistic son Basil.