Young Mary follows a mysterious cat into the nearby forest and discovers an old broomstick and the strange Fly-by-Night flower, a rare plant that blossoms once every seven years. Together, the flower and the broomstick whisk Mary above the clouds, and far away to Endor College -- a school of magic run by headmistress Madam Mumblechook and the brilliant Doctor Dee. But there are terrible things happening at the school, and when Mary tells a lie, she must risk her life to try and set things right.