A fantastic story, delightfully dark and emotional. There's so much here that sticks with me; the chess puzzle, the Doctor's betrayal of Ace, vampires being repelled by Communism -- it's a really intricate, well-crafted story. If you don't like a darker, more manipulative Doctor, you won't care for this one, but if you do? It's great.

Also the subtle moment about the Doctor's absolute faith in his friends and companions makes me go a little crazy. Love that for him.