The story opens in London, 1916, but not the London we remember. World War I has been subtly twisted by temporal contamination. The Doctor, still carrying Molly’s "Dark Eyes" device, encounters a new face: Liv Chenka (played with sharp precision by Nicola Walker ). Liv is a medic from the future—a pragmatist who has no time for the Doctor’s brooding. Their initial chemistry is hostile; she calls him out on his arrogance, and he dismisses her logic. This episode masterfully introduces the Master (in his pre-Delgado, scheming incarnation played by Geoffrey Beevers ) as a reluctant ally. The twist: The Traitor refers not to the Master, but to a version of the Doctor himself.