Helena, a 15-year-old girl in a family of circus entertainers, often wishes she could run off and join real life. After a fight with her parents about her future plans, her mother falls quite ill and Helena is convinced that it is all her fault. On the eve of her mother's major surgery, she dreams that she is in a strange world with two opposing queens, bizarre creatures, and masked inhabitants. All is not well in this new world - the white queen has fallen ill and can only be restored by the MirrorMask, and it's up to Helena to find it. But as her adventures continue, she begins to wonder whether she's in a dream, or something far more sinister.