Following immediately on from Leela's first appearance, this story see the TARDIS deposit the Doctor and his new companion on a sandminer. Someone is killing the crew one-by-one, and the travellers are the first suspects...
Sort of like I, Robot meets Dune on the Orient Express, the story is a science fiction murder mystery with the characters each having backgrounds that allow for most anyone to have done it.
The main problem with the book is that you are deprived of the wonderful costumes and sets that greatly enhanced this story on TV. This story was sensibly selected as an early video release, and is also one of the earliest DVD releases, so you know it is held in high regard.