Martin Chisom has been busy moving rhubarb into the forcing shed. He ponders the almost ritualistic actions his work entails. Suddenly, he hears a sound — a sound he finds, as his sister told him, is that of the rhubarb growing. He notices that the sound indicates he is being surrounded and when he tries to run, is constrained.
The Third Doctor and Jo Grant walk up a path after seeing a sign advertising the sale of rhubarb. Knocking on the door, a woman answers and asks the Doctor if he is a medical man. He answers in the affirmative and is invited in. The Doctor is shown Chisom who is sweating feverishly under his bedsheets. He was found by Brian and Claire Forest.
The Doctor places a plaster on Chisom which calms the man's thrashing and warns that something is wrong with their rhubarb. Only now does he realise Jo is no longer next to him. Brian tells him that the "student nurse" has gone down to the forcing shed. The Doctor runs to the shed, leaping several stairs as he does.
The Doctor enters the shed and is followed by Brian. The snapping noise begins and the Doctor lights a candle. The noise stops and the Doctor uses the light to reveal to reveal a "red metal bug about the size of a cat". The creature screeches with an ever increasing pitch. It then begins to speak, saying it claims "this world by right of conquest", before correcting itself stating "this shed belongs to us". The Doctor replies that "that sounds altogether more reasonable".
Later, having been united with Jo, who admits that she got lost and went to the wrong shed, the Doctor relates the resolution to the situation. Brian and the alien reached a trade agreement wherein Forest would supply manure in return for "the tenderest rhubarb in the galaxy, grown at a rate unheard of on Earth."
Jo asks if this is irresponsible, but the Doctor assures her that the aliens are quite happy in their shed before remarking that they have all the the ingredients they need for a "near-perfect" rhubarb charlotte."
- Martin Chisom grows rhubarb in a forcing shed. Due to the plants' delicate nature, he uses candles as a light source.
- The stands his candles are placed upon give the shed a medieval look.
- The Doctor uses his everlasting matches.
- The Doctor suggests negotiations over a cup of tea.
- "Agoraphobic micro-aliens from a compact dimension" is the description the Doctor gives Jo of the bug.
- Martin mentions trying to phone Brian, only to discover him in the farm when they hear his phone ringing, possibly placing this story in modern times.
- The Doctor uses his Promethean Everlasting Matches. (PROSE: Venusian Lullaby, et al.)
- The Doctor contemplates wearing rhubarb in his lapel, but dismisses it as being too garish. The Fifth Doctor wore celery on his own lapel. (TV: Castrovalva)