This was a fun concept for an episode that sadly suffers a bit in the execution of its own ideas.  I really liked the idea of setting this story deep into the French Revolution.  The writer Dennis Spooner and director Henric Hirsch do a very good job at painting a picture of what this time period was like - the fear, paranoia, and authoritarianism are all well expressed and even explored here.

Sadly, most of these episodes consist of a lot of talking in very confined sets.  It really doesn't feel like the show had the budget at this time to really show off Paris in 1794.  The costumes are well done, at least.  It feels like the companions (especially Susan) don't have much to do here compared to the Doctor, but at least William Hartnell gets to be very present and involved in this story.  I like his dilemma and debating about how much he can and should get involved in events and they do a very good job at following up on his opinions in The Aztecs.  All in all, I'm glad I watched these, but definitely think it came up a little short in a few key aspects that prevent The Reign of Terror from being a classic on the level of The First Doctor's better stories.