The plot is essentially a murder mystery of the type where a group of people in an isolated location must determine which of their number is a murderer before he (or she) kills them all. The twist is that the isolated location in this instance, rather than the traditional English country house, is a mobile mining facility on a distant planet, crewed by a small number of humans and a rather larger number of robots - a point which is made relevant when it becomes clear that the murderer is capable of turning the robots against their masters.
The story was written by Chris Boucher and directed by Michael E. Briant. The cast also includes Russell Hunter, Pamela Salem, David Collings, Brian Croucher, David Bailie, Rob Edwards, Tania Rogers, and Tariq Yunis as the crew of the sandminer, and Miles Fothergill and Gregory De Polnay as members of the sandminer's complement of robots.
See also List of Doctor Who serials