First appearance of Mel played by Bonnie Langford, she remains as of 2007, the only companion (excluding Susan, the First Doctor's granddaughter) without the typical "meeting" story.
Designed as a typical Agatha Christie murder mystery set on a space liner, the actual structure of the story (and its bubbly tone) are reminiscent of the series during Douglas Adams' tenure as script editor, during season seventeen. In the first episode, Professor Lasky is briefly seen reading a copy of Christie's "Murder on the Orient Express".
This would be the last time in the series that Colin Baker would be seen in the TARDIS console room, as Sylvester McCoy stood in for him in the regeneration scene of Time and the Rani: Part One (1987).
Because script editor Eric Saward had resigned in an well documented row with John Nathan-Turner, there is no Script editor credit for esp 9,10,11 and 12 of this story . Nathan-Turner worked as script editor.
This four-part story within the Trial of a Time Lord season is commonly known as "Terror of the Vervoids".