The Doctor, Ace and Bernice arrive near a moonbase and meet a woman named Jen Yates; when she asks them if the Human-Earth Reptile war is still being waged, the Doctor seems ill at ease, but to her relief informs her that humanity won.
Jen invites them inside the base and tells them that she was a singer responsible for entertaining the troops, but was later conscripted into the war and put in charge of the weapon situated at the base. The Doctor sets about repairing Carl, the station's robot who was blinded in an accident; meanwhile, Ace deactivates the station's weaponry, and Bernice discovers an unborn baby held in stasis inside Jen's room.
Jen becomes increasingly anxious of her visitors, and questions their information concerning the war; she finally snaps, turns off the lights and then uses night-vision goggles to locate and then attack Ace. But Carl interrupts their fight and attempts to kill Jen; Ace manages to shoot the robot, and the Doctor stops Jen from killing Ace by threatening her baby — an act that shocks Jen into remembering that she not human, but is in fact an Earth-Reptile.
"Jen" recalls that she is actually a soldier named Qurra, who single-handedly killed the station's human crew; however, one of the humans, a woman named Jen, managed to activate the weapon situated there before she died, killing everyone on the planet below.
Traumatised by the countless deaths that she caused, Qurra's mind snapped, and she took on the identity of Jen, blinding Carl so he would be unaware of her true race. Wracked with guilt, Quarra walks onto the lunar surface to her death before the others can stop her. The Doctor leaves Jen's baby with a human couple on a remote Earth colony.
- The station housed members of the Zara Seven Colonial Army.
- The stories in Short Trips: Steel Skies are divided into four sections dealing with different types of confinement. This story deals with isolation, that is, "the loneliness and despair of being cut off from the world outside".
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