When an evil man claiming to be their uncle removes them from an orphanage, Tony and Tia, siblings with unusual powers, run away and try to find other people like themselves in hopes of learning something of their mysterious past.

Tia and Tony are teenage sister and brother who possess extraordinary powers. They leave their safe refuge on Witch Mountain for a trip to Los Angeles. There, Tony is kidnapped by the evil Dr. Gannon and his spinster partner Letha. Tony is brainwashed into helping Gannon and Letha commit various crimes. It's up to Tia and a gang of juvenile delinquents to rescue Tony and prevent a major disaster.

Two young orphans with supernatural powers are adopted by a powerful and ruthless millionaire who plans to hold them captive and use their psychic gifts for his own selfish purposes. The children make a daring escape and learn they are actually castaways from another world.