The Doctor and Leela visit the human race during a period where they have migrated to Pluto and become enslaved by the bureaucracy and the taxes of the Collector.
Laden with considerable jokes and allusions to taxes and the inland revenue that lack subtlety, this story often feels like it is not really being taken seriously enough considering its Orwellian nature and some of its subject content. The death of the Gatherer, for example, in the televised version was a scene that was treated in far too a light-hearted manner that it felt a little wrong. Dicks re-addresses this in the novelisation by providing an insight into the motivations of those involved. This makes it clear that at least some of them are regretfully doing what they deem necessary rather than just having fun killing someone. At its best though the script possess some Aristophanic style and elements.
This is a story focussed more than most on the Doctor toppling a totalitarian state; and this is one of the Doctor's greatest strengths. It is a good example of how the Doctor's presence can act as a catalyst against oppression.
There is a fine selection of well crafted characters that ranges from corrupt capitalist exploiters to the everyday man on the street. Dicks duplicates them well from the Holmes originals. There is also plenty of witty dialogue if the references to taxes don't become too much. Fun as it can sometimes be, there are times in this story where perhaps the wit and the parody overshadow the plot and the action.