A pretty inoffensive two-episode story. It's a nice change of pace to get the rare story that's filmed entirely outdoors in some scenic rocky terrain. The first episode doesn't do much with us meeting some stranded astronauts with a machine following them. It picks up more when we meet the Sontaran, but the story consists of a lot of 'Sontaran pops up with these characters, then with this characters, etc'. The Doctor tiring out the Sontaran is pretty fun. Overall, an inoffensive story but nothing memorable.