John has fallen through a forgotten door to the strange planet Earth and is in great danger. Soon the family who befriends him is in great danger too. Time is running out. He must find the secret passage quickly or he may never get home.

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.