Sky Silvestry

Sky Silvestry is a passenger and a businesswoman aboard a tourist craft going around the planet Midnight. She explains to the Doctor that she is visiting the planet after the end of her relationship with her female partner.

When an unknown force begins banging on the side of the vessel, Sky panics, in the belief that her former lover has returned to get revenge. The force, apparently feeding on her fear, possesses her (it is not know if any of her consciousness remains afterwards).

While possessed, Sky repeats everything that everybody says, until moving onto the next stage of saying the same thing at exactly the same time. The other passengers become extremely disturbed by this and decide they want Sky thrown off the bus to her death, which the Doctor objects to. While being spoken to by the Doctor, Sky steals his voice and manages to make him start repeating her, leading the other passengers to believe the lifeform has left Sky and has now possessed the Doctor, but in reality, Sky is still possessed, just progressing.

As Sky convinces the others to chuck the Doctor off the bus, the Hostess realises Sky is still possessed, grabs her and opens the door and is sucked out with Sky, sacrificing herself and Sky to save the Doctor. (DW: Midnight)

Behind the Scenes
It is said that when the force inside Sky was talking of "He has been waiting in the darkness, in the cold..." and of people who feel pain, she may have been referring to Davros. How the entity knew of Davros and his return, is, as of yet, unsure. This episode is before Turn Left, the episode leading to, or possibly including the return of Davros, such a rumour would be perfectly placed.