The TARDIS has materialised in a spherical chamber. It is dark in the corridors outside, and Steven thinks they have materialised inside a ship. Bringing torches, the Doctor, Steven and Vicki leave the TARDIS to explore.
They find a plasma generation circuit and wonder what it could be doing here. Suddenly there is a flare of light further down the corridor, and Steven thinks he sees two figures welding something. He hears them running away, and they make their way to the place in question. As the Doctor and Steven examine the monitor on the panel, Vicki goes further down the corridor. She falls through a hole in the floor. Steven goes down the chute after her, while the Doctor stays behind.
Steven loses his torch on the way down the chute, and when he finally lands, he hits his head and blacks out.
When he wakes, Vicki is waiting for him. They are in a huge factory room, near the "spaceship" in which the TARDIS materialised. It is dark, and the floor is littered with parts. Vicki says the workers, whom she calls "handymen", are quite friendly, though they don't speak. Taking a good look at the "spaceship", Steven realises it is in fact a space cannon, and the Doctor and the TARDIS are still inside.
The foreman leads Steven and Vicki to a control room. He shows them a screen indicating that a ship is approaching. Steven and Vicki deduce that the workers have built this weapon to use against their enemies, who will soon arrive. The weapon is nowhere near ready, and Vicki convinces Steven to help the workers finish it.
Several hours later, the weapon is finished, the factory floor is clean, and the room has been lit. Some of the workers even retrieved the TARDIS from inside the weapon. The Doctor soon arrives, and scolds his companions for helping with such a terrible weapon. He has discovered that the weapon was a job commissioned by another species and that the workers are awaiting, not their enemies, but their clients. The Doctor hurries his companions into the TARDIS, and they watch events outside on the scanner. The handymen's clients arrive, and are revealed to be humans.
- The Doctor keeps torches in a trunk.
- The stories in Short Trips: Steel Skies are divided into four sections dealing with different types of confinement. This story deals with flight, that is, "travellers who left their homes for far-away destinations".
- Vicki continues her habit of giving nicknames to alien creatures. (TV: Galaxy 4, PROSE: Planet of the Bunnoids)