It was an accident. A time warp, a time stream, something that took her away from us. She went through the wrong door, wandered into a room never intended to be opened, touched something never meant to be touched… and when we brought her back we miscalculated. Something went wrong. And it’s been ten years. Twenty. Thirty.
Mollie, the eight year old daughter of the station’s chief engineer and his botanist wife, wanders into a cave and activates a time distortion field built millennial ago. She falls through, and her father arrives too late to save her. Scientists beam down and they determine that she’s been hurled back three hundred years into the past at a time when the planet was completely uninhabited. They work hard to reactivate the field, intending to bring her back barely moments after she fell through.
Working with alien technology is difficult, and when they bring her back through she’s a wild, uncontrollable eighteen year old who doesn’t remember how to speak, who she is, or why she’s suddenly be snatched away from “home.”
It’s a quarantine facility, but they didn’t figure that out until later. The door has two buttons, a red waterfall and a green anchor. The buttons lead not to separate rooms, but separate time streams. The red waterfall takes Amy to compressed time stream; a place where years pass in a matter of days.
The Doctor sends Rory in to get her, planning on getting her out just a few hours after she went through, but something goes wrong, and it’s been thirty years. Thirty years alone in a quarantine facility, waiting for a rescue that never came, fighting off helpful robots who’s medicine will kill her, Amy is old, bitter, and almost as uncontrollable as Mollie.
Both episodes are very similar. In both those who are left behind, the girl’s father, mother, husband, they want their girl back, not the one they got. They want what they lost, the young, innocent and loving child. They both struggle with this person who is the same, yet not the same…
But they deal with the subject in very different ways. In DS9 the idea of trying again is instantly rejected. “Just because we missed those ten years of her life doesn’t mean we have the right to take them away.” In Doctor Who they do everything they can to bring back the younger Amy, and it leaves open for discussion the obvious question of whether what they did was moral or not.