Doctor Who: The Reign of Terror directed by Henric Hirsch, written by Dennis Spooner
First Doctor William Hartnell tries to return Ian and Barbara to England in their own time. He misses by a hundred miles and lands outside of Paris. He also misses by two hundred years and arrives in the middle of the Reign of Terror (which is the guillotine-iest part of the French Revolution, in case you don't know). The Doctor and his companions (including granddaughter Susan) are soon caught up in the political intrigues of Citizen Robespierre's worst days (which naturally involves a lot of prison time for the characters).
The story is interesting with the usual turns of luck for the Doctor and his friends. The nice blend of humor and drama is kept up, with Hartnell being especially silly in his period costume. They even manage to have one or two thoughtful conversations about both sides of the French Revolution and England's role during it. The original broadcast was in six episodes, though the videos for episodes four and five are lost. The audio still exists and some rough animations have filled in. The animators had plenty of reference material from the other episodes but it looks a bit jarring. Even so, watching the animations is definitely preferable to listening to the audio by itself (all those action scenes without dialogue would be hard to understand).