Carmen (Planet of the Dead)

Carmen was a middle aged woman, married to Lou, who was onboard the London Bus Number 200 with the Doctor and Lady Christina de Souza.

Carmen had low-level psychic abilities. She was able to predict future events (every week, twice a week, she and Lou would win ten pounds on the lottery), sense what was going on without her seeing it, and hear the voices of the dead on the planet. After the Doctor saves her, Carmen tells him, "Your song is ending... it is returning through the dark... and ... oh, but then.... he will knock four times."(DW: Planet of the Dead) This lead to speculation that the master was returning (later confirmed by the BBC).