UNIT HQ is attacked by soldiers in unfamiliar uniforms, who capture Liz and take her through the interface into the other timeline. The Doctor knows that she will only survive for a short time on the other side; she is currently imbued with artron energy due to her trip through the time bridge, but as that decays she will slowly cease to exist. The Doctor, the Brigadier and Benton set off after her, using the fragment of Brokk's ship from the time bridge as a portable artron energy reserve. Yates and Osgood remain on guard as the soldiers outside begin to bomb UNIT HQ; their bombs fade away on UNIT's side of the interface, but are slowly becoming more real—and more dangerous.