The Doctor and Peri are running down a corridor, chased by N'Tian soldiers who are firing at them. They turn a corner and come to a lift. It works too slowly for them, as they can hear the soldiers approaching. The Doctor spies the entrance to a ventilator shaft, and they hide in there as the soldiers approach.
The Doctor and Peri head down the shaft, which empties into a chamber, a distribution node, with three large, wall-sized fans. There are ladders leading to holes in the ceiling. Peri is starting to regret travelling with the Doctor.
The Doctor chooses one of the ladders, and they begin climbing. At one point, the Doctor stops, frightened. Peri is amused to learn that the Doctor is afraid of the spider that is blocking their path. She moves the spider and they continue.
At a fork, they turn into the left shaft, hoping to find another distribution node. They hear a clang in the shaft, and the Doctor realises that it is a service drone. It detects their presence and follows them down the shaft.
They come out into another distribution node, but this one is a dead end. The Doctor uses Peri as a decoy. When the drone arrives in the chamber, it heads for Peri. The Doctor throws two cricket balls its way, confusing it, and covers its sensors with his hat. He jumps on its back and begins to pull at various wires inside it.
The drone manages to remove the hat and begins choking Peri. Just in time, the Doctor removes the correct wire, stopping the drone. Peri starts to cry, and the Doctor tells her he will take her home, that no one travels with him against their will.
Suddenly they hear a hissing sound. The room is filling with sterilisation gas. Their only escape is the shaft they came through. They return through it, but the gas is too fast. Out of the shaft, they have to decide which way to go while the gas increases. The Doctor sees a spider, but this time his fear is replaced by delight, as he sees it join several other spiders that are escaping the gas. They follow the spiders and eventually make it to the surface.
Once Peri recovers her breath, she looks around her. It is dusk, and the ground is full of Pilgrim's Lanterns, glowing flowers that only grow on N'Tia. She also sees N'Tia's beautiful fourth moon. She decides that she will travel with the Doctor after all.
- The Doctor and Peri were on their way to see Boycott score his hundredth hundred.
- Instead, they accidentally stir up a rebellion between the N'Tians and their slave workers.
- The Doctor has always wanted to see Les Mis.
- The stories in Short Trips: Steel Skies are divided into four sections dealing with different types of confinement. This story deals with frontiers, that is, "the corridors, living quarters and ventilation shafts of four futuristic environments".
- The Doctor is scared of spiders. (TV: Planet of the Spiders, PROSE: Return of the Spiders)
- The last time Peri felt this miserable was on Sarn — which was only a couple of days ago. (TV: Planet of Fire)