Escape to Witch Mountain

A 1968 Science Fiction novel by Alexander Key, who also wrote The Forgotten Door. It has been made into a film by Disney three times, in 1975, 1995 and 2009.

Tony and Tia Malone are decent, intelligent kids, but have a bad record, partly because they have grown up in a slum, and partly because Tia ignores rules and common sense whenever she sees an animal in distress (she once broke into a store to free a trapped kitten, so she has a record).

They conceal the fact that they have Psychic Powers, and that Tia can talk (her voice is pitched beyond the range of most people's ears, other than Tony's).

They do not know where they originally came from; they have lived with Granny Malone, who was struck and killed by a car the day before the story opens. Because of their record, they are then packed off to an Orphanage of Fear, and begin trying to make a serious effort to remember their past. Their only clue other than their own memories is Tia's "star box" - a leather box on a strap with a curious double star design on the lid, which she has had as long as she can remember and which she always carries (since it contains the pencils and paper she uses to communicate with people other than Tony). A chance encounter with an elderly nun gives them another clue - she recognizes the design on the box as something she once saw on the letterhead of a letter, looking for children with "unusual abilities". She cannot quite remember who wrote the letter, but from what she does remember, the children eventually come up with the name "Castaway".

Tia later finds a map to Witch Mountain - which is in the Blue Ridge Mountains - and a lot of cash concealed beneath a false bottom in her "star box".

Matters come to a head when a man comes to the Orphanage of Fear claiming to be their uncle - Lucas Deranian, whom Tia recognizes as the man who originally left them with Granny Malone, and who she dislikes and distrusts on sight. The kids run away after being told that he is now their Illegal Guardian, heading for Witch Mountain. When they finally reach their destination it's discovered that they where originally from an alien planet. They had to come to earth to survive a planet-wide disaster, so the grownups built a colony on Witch Mountain.

In the sequel, the slightly older Tia and Tony are now on vacation. They arrive at Los Angeles for a visit. When Tony uses his powers to prevent an accident, he gets into the hands of Dr. Gannon, a ruthless scientist who's constantly striving for power over the world. He puts a device into Tony's brain that allows him to control his will. Tia gets help from a kids gang to free Tony and save the Earth.

Tropes seen in this story and its adaptations include:

 * Alien Among Us: What the Castaways turn out to be.
 * All of the Other Reindeer
 * Alternate Continuity: The Beyond Witch Mountain film ignored the first sequel.
 * Animated Credits Opening
 * Badass Preacher: Father O'Day.
 * Bald of Evil/Beard of Evil: Bolt and his henchmen have one or the other.
 * Big Bad: Aristotle Bolt
 * Big Brother Instinct: Tony in the movie.
 * Chekhov's Gun: During their escape in the film, thunderhead and the gate guard's cat allergies.
 * Children Are Innocent
 * Corrupt Corporate Executive: Bolt.
 * Cute Kitten: Winky in the film.
 * The Dragon: Lucas Deranien
 * Everything's Worse with Bears: Averted; the kids use a bear to help them escape from Bolt's henchmen.
 * Friend to All Living Things: Tia.
 * Green Aesop
 * Grumpy Old Man: Jason O'Day in the film, becomes Cool Old Guy
 * Hair of Gold: The twins in the movies.
 * Half-Identical Twins: Tia and Tony
 * Heartwarming Orphan
 * Human Alien
 * Humans Are Bastards
 * Illegal Guardian: Lucas Deranian
 * Magic Music: Tony's psychic powers are a lot stronger when he plays his harmonica.
 * Moses in the Bulrushes
 * No Good Deed Goes Unpunished: The twins catch Bolt's eye after they save one of his men.
 * Orphanage of Fear
 * Orphan's Ordeal
 * Orphan's Plot Trinket: the star box
 * Parental Abandonment: The kids' only guardian was killed in a car accident the day before the story opens.
 * Pink Girl, Blue Boy: In the movie, Tia's bed is decorated pink.
 * Psychic Powers: Tony can visualize far away places and see what is happening there. He and Tia both have telekinesis (although hers is mostly used for opening locks).
 * Mind Over Matter
 * Seers
 * Speaks Fluent Animal
 * Telepathy
 * Super Human Trafficking
 * Surveillance as the Plot Demands
 * Trauma-Induced Amnesia: Although Tia has a near-perfect memory, she cannot remember anything prior to their arrival at Granny Malone's.
 * Unusually Uninteresting Sight: In the movie, anyway, the kids at the orphanage seem to get over the shock of seeing psychic powers very quickly.
 * Witch Hunt