It’s called “Return to Oz” and not surprisingly was much less successful than the original. The story goes that six months after returning, Dorothy has trouble sleeping and is obsessed with her adventures from Oz. Her aunt and uncle are extremely disturbed because they see their niece as closer to insane than creative.
They take Dorothy to a doctor where she is treated by various techniques, including electric shock therapy, before she almost drowns and wakes up in Oz once again. Oz is in ruins and a war of sorts is going on. Dorothy and a fellow mental patient traverse the lands and meet a host of new characters before setting things right and returning to Kansas.
The movie received mixed reviews, but was generally labeled as more dark and creepy. However, like most strange movies, it has since gained a cult following.