The movie centers upon the brother and sister pair Tony and Tia, who initially know only their deceased adoptive parents' surname, Malone. The children are placed in an orphanage, where they face difficulties stemming from their strange psychic powers. Tony can telekinetically move objects with the aid of his harmonica, and he can experience a limited form of premonition as shown in the scene where he draws Mr. Bolt's mansion on a mirror. Tia can communicate telepathically to Tony, commune with animals, experiences premonitions, and can also use minor telekinetic powers (which are much stronger in Return from Witch Mountain). She carries a "star case" with her at all times, which the children find contains a strange map.
Tia has fragmented memories of her early childhood, including an accident at sea and a man she later remembers as the children's Uncle Bené (pronounced Ben-ay), whom they believe drowned during their rescue.
During a field trip to see a movie, Tia experiences a premonition and is able to warn wealthy attorney Lucas Deranian against a potentially dangerous accident. Deranian informs his employer, millionaire Aristotle Bolt, of the children's powers. Bolt, obsessed with the paranormal, demands that Deranian retrieve the children at all costs. Deranian's detective work leads him to the orphanage, where he poses as Tia and Tony's uncle, though not under the name Bené, and takes them to Bolt's mansion.
Though initially suspicious of Bolt's motives, Tia and Tony are lured in by the wealthy trappings of Bolt's home. Bolt eventually reveals that he has been monitoring the children via a closed-circuit television system and that he and Deranian are fully aware of their powers. The night of this revelation, Tia and Tony make an escape, making use of their powers to control a wild mustang, guard dogs, and the security fence.
Bolt sends Deranian and a thug, Ubermann, after the children. Tia and Tony hide out in a Winnebago motor home owned by a crotchety widower named Jason O'Day (Eddie Albert). Initially negative towards the children, Jason gradually begins to recognize their powers and the truth of their story; Tia's vague memories of a disaster at sea intrigue him. He agrees to take the children on the route indicated by Tia's star case, which leads them to a mountain known as Witch Mountain, home to unexplainable phenomena. Avoiding Bolt, the law and an incited mob convinced the children are witches, they eventually make their way up Witch Mountain, pursued by Deranian and Ubermann as well as Bolt in a helicopter.
As their memories begin to fully return, the children realize their accident at sea did not involve a boat, but a spacecraft. Tony and Tia are actually of extraterrestrial origin; the double star emblem on the star case stands for a binary star system where their home planet was located.
Having come to Earth because their own planet was dying, survivors of the journey made their way to Witch Mountain and formed a community to await the surviving children, each pair in possession of a star case to help them find their way to their new home. Tony and Tia are the first to reach their destination. The children are reunited with their Uncle Bené and board another spacecraft. When Bolt and the others leave in defeat, Jason witnesses the ship's return as it flies over him to say a final goodbye.
- Eddie Albert as Jason O'Day, an embittered widower who decides to travel across the country in his green and white Winnebago.
- Ray Milland as Aristotle Bolt, a ruthless and greedy multi-millionaire obsessed with the paranormal and occult who intends to exploit Tony and Tia's powers to increase his wealth.
- Donald Pleasence as Lucas Deranian, a well-to-do attorney who works for Mr. Bolt.
- Kim Richards as Tia Malone, a nine-year-old orphan with premonition or psychic powers and limited telekinesis.
- Ike Eisenmann as Tony Malone, Twin brother to Tia, orphan with telekinetic powers and limited premonition.
- Walter Barnes as Sheriff Purdey, a sheriff bribed by Bolt to pursue the children.
- Reta Shaw as Mrs. Grindley, owner of the orphanage Tia and Tony are sent to after the death of their foster parents, the Malones.
- Denver Pyle as Uncle Bené, the children's true uncle.
- Alfred Ryder as Astrologer.
- Lawrence Montaigne as Ubermann, a henchman who assists Deranian in his pursuit of the twins and drives his Lincoln Continental limousine.
- Terry Wilson as Biff Jenkins.
- George Chandler as Grocer.
- Dermott Downs as Truck, a child from the orphanage who bullies Tony to the point that Tony reveals his powers.
- Shepherd Sanders as Guru.
- Paul Sorenson as Sergeant Foss.
- Alfred Rossi as Police officer.
- Tiger Joe Marsh as Lorko.
- Harry Holcombe as Captain Malone.
- Sam Edwards as Mate.
- Dan Seymour as Psychic.
- Eugene Daniels as Cort.
- Al Dunlap as Deputy.
- Rex Holman, Tony Giorgio as Hunters.
- Kylie Richards, as young Tia Malone (in "elder Tia's" memories)
Movie / Book Differences
Escape to Witch Mountain is based on the novel by Alexander Key. Significant differences from the book include its tone and plot elements. For example, in the book, the children are befriended by Father O'Day, an embittered inner-city priest, rather than widower Jason O'Day. As such, the novel touches on religious themes, while the movie completely avoids them. In the novel, instead of the children's ship crash-landing, it is shot down, and the children are olive-skinned, with light-colored hair, rather than fair-skinned and blond. In the book, Deranian is the main antagonist; the Aristotle Bolt character and his associates are absent. The novel is explicitly set along the east coast of the United States, while the movie is non-specific about the location, although it was clearly shot at various locations on or near the California central coast between San Francisco and Santa Barbara.
Main article: Escape to Witch Mountain (1995 film)
The movie was remade in 1995 with a different cast and several details changed or omitted. In the remake, Tia and Tony are twins, renamed Anna and Danny. They are separated as children, but reunite in an orphanage where they discover their powers. In the remake, Bolt is a land magnate who wants to develop Witch Mountain, using the twins' power to do so. The children are rescued by a shopkeeper.