Planet (The Caretaker)

The Twelfth Doctor and Clara Oswald were once held prisoner on an unnamed desert planet. While chained to a post, the Doctor told Clara to pass him the vibro-cutters so they could break free, only to be informed by her that she had left them in the pocket of her other jacket which she left at home. (TV: The Caretaker)

Behind the Scenes

 * It is never explained how the Doctor and Clara came to be held prisoner on the planet nor how they eventually escaped.