The Doctor and Leela land inside a desert planet-traveling futuristic drilling/mining machine being run by a racially-diverse yet argumentative crew and a shitload of cool-looking robots. One crew-member turns up dead so they blame the two unknown and newly arrived people - the Doctor and Leela of course. As the story unwinds, more crew-members die like something from an Agatha Christie story and things look dire when Tom Baker is buried in dog chow. I'm not gonna spoil this one for you because it's too fun to watch.