Tia (Kim Richards) and Tony (Ike Eisenmann) Malone are two youngsters who live in an orphanage and have extraordinary powers (including ESP, precognition and telekinesis).
Lucas Deranian (Donald Pleasence) forges adoption papers and poses as their uncle in order to get the kids into the clutches of his megalomaniacal boss, evil millionaire industrialist Aristotle Bolt (Ray Milland), who wants to exploit them.
Jason (Eddie Albert), a cranky and cynical old widower, helps Tia and Tony escape to Witch Mountain to try and find out where they came from and discover the secret of their extraordinary powers.
This all leads to a climactic chase where the children’s mysterious “family” – a race of humanoid aliens that have migrated to Earth – reveal their true powers.
The film was a hit for Disney and led to a sequel (Return From Witch Mountain) in 1978, as well as a 1982 TV pilot (Beyond Witch Mountain), a 1995 TV movie and a 2009 sequel (Race To Witch Mountain).