After having a rough day (compounded by a massive wart appearing on her forehead), Sabrina escapes into the mirror in her room to get some peace and quiet.But when she wants to leave, she discovers that her bad mood has sealed her within the mirror world, where everyone is as grouchy and grumpy as her.But when her trophy starts calling her a cheater, she gives the previous champion a rematch so he can get the honor he deserves.
A rude and condescending math teacher punishes Sabrina for asking a question by giving the whole class a difficult test.
When Sabrina does poorly, both Hilda and Zelda try to reason with him--and fail.
Sabrina gets a surprise visit from her Aunt Vesta (Raquel Welch), Hilda and Zelda's older, and much less responsible, sister.
Vesta shows Sabrina the fun side of being a witch, and later tricks Hilda and Zelda into letting Sabrina stay with her at the "Pleasure Dome," her home in the Other Realm.
She must then hide the truth from Rudy's parents and deal with a full-grown adult that has the mind of a toddler.