I hadn't realised, but there are actually two Doctor Who stories with the title Relative Dimensions. The first is the 8th Doctor audio released by Big Finish; the second a 12th Doctor comic from Titan.

So, the audio first. This is an odd story. It features the 8th Doctor, Lucie Miller, Susan and Alex, her son (the Doctor's great-grandson). Alex had been introduced in the story An Earthly Child. Lucie has just returned to the TARDIS after leaving the Doctor because of the events in Death in Blackpool. In between, he had been travelling with Tamsin, who has now gone off with the Monk. Lucie leaves the Doctor again at the close of this story only to return, along with Susan and Alex in the season's finale (Lucie Miller/To the Death). It's a lot of coming and going and makes this story a little difficult to listen to out of context.

To make matters worst, it's really, really boring.

The Doctor has invited Susan and Alex for Christmas dinner. Lucie is on cooking duties. However, an airfish, bought by Susan on Quinnis and left dormant all these years in her room, is suddenly resurrected. It goes on a rampage, flying around the TARDIS and slipping between dimensions and timezones. Eventually they catch it and release it into its natural habitat. The end.

Relative Dimensions is by the usually reliable Marc Platt, but I reckon he dropped the ball on this one. The dialogue between the four characters isn't great and Carole Ann Ford's performance doesn't really help - one minute she's angry with the Doctor, the next she sounds like she's had too much sherry. Sheridan Smith is given hardly anything to do except witter on about gravy. Jake McGann is okay as Alex but has a bit too much petulant teenager written into his character. Paul McGann is solidly reliable but, like Smith, isn't given much to work with.

The link with Quinnis (a Companion Chronicle featuring Carole Ann Ford) is also a bit odd. It's a throwaway reference in that story that is expanded on here (figurativelyand literally) into a flying, monster fish. Both these stories were released at the same time, so Platt obviously decided to cross-reference them during the writing process, but whether the airfish was part of Dimensions first and inserted into Quinnis or the other way round, I'm not sure. Either way, it's not the most convincing of Doctor Who monsters.

There's not a huge amount more to say on this story as there's not a huge amount to say anything about. As Doctor Who stories go, it's not one I'm in a hurry to return to, although ironically, if marathoning the 8th Doctor audios it is quite important in setting the pieces in place for the final story of the season.