Mary Smith, a red-headed girl with a penchant for mishaps, moves in with her Great Aunt Charlotte and finds herself bored and lonely. However, her routine changes when she notices a cat that transforms its color every time she sees it. Intrigued, she chases the cat into the woods where it leads her to a strange clearing with dead trees and brown grass. In the middle, she finds a cluster of blue flowers that she's never seen before. Mary learns that the rare plant is called "Fly-by-Night," which witches desire for its potent magic. When she follows the cat once again to the woods, she discovers an old broomstick hidden behind a gnarled tree. Clumsily, she smears Fly-by-Night on it, and it suddenly glows, carrying her away into the sky. She then lands at Endor College for Witches, and the students there mistake her for a new pupil. Mary must learn to fend for herself in a world of magic where things aren't always what they seem.