Return from Witch Mountain (1978)

"Sinister forces from this world against two young space travellers from another."

Tony and Tia are other-worldly twins endowed with telekinesis. When their Uncle Bene drops them off in Los Angeles for an earthbound vacation, a display of their supernatural skill catches the eye of the nefarious Dr. Gannon and his partner in crime, Letha, who see rich possibilities in harnessing the children's gifts. They kidnap Tony, and Tia gives chase only to find Gannon is using her brother's powers against her.