Anyways even though its basically just a slideshow it still comes across very well. I treated it almost like a comic book because in certain scenes text would show up telling you what action was happening on the screen. I love to read, and thanks to being used to text boxes in RPG's I think, I was still able to enjoy the story.
It is just genius how they used Marco Polo in this. He is like a early adventuring superhero. You wanted to see how this serial played out because how he has put his trust in the bad guy. And the bad guy tries to stick it to old Marco many times through the episode. So by the time we see the final battle where they finally lock swords your totally wanting to see the bad guy get what's coming to him.
For more information go here: http://en.wikipedia.org/wiki/Marco_Polo_(Doctor_Who)