Remember how I talked earlier about learning the history of the Hashishin from the novelization of this story? And remember how it took pride of place on my bookshelves, and I kept it long after the rest of my Target novelizations were let go to clear space on my bookshelves? Well, I have to say that it was a good thing that Lucarotti got to write that Target novelization, because as good as this is as a final episode, he didn't quite stick the landing here.
Don't get me wrong, this is a great episode. It gets off to a fast and exciting start, with Tegana getting a great villain speech (and again, it's awesome that his superstition isn't used to make him seem foolish, and in fact more of a threat) and framing Ian for the theft of the TARDIS. At this point, it must be said that Tegana has had a lot of unearned luck, here--he wasn't the one to kill Kuiju, and if either the guards had overheard him boasting about making Noghai the ruler of the world or if the guards hadn't been overzealous and Kuiju had fingered him, this would have been a very short episode seven. But you can say the same thing about any long story with a villain, really. ('Under the Dome'--the novel, not the TV show--has the same problem.) Still, it's a solid scene, made more so by Derren Nesbitt's silky smooth performance.
Then we get a wonderful highlight of the story--the Doctor and Kublai Khan's backgammon match. The sequence where the Doctor totals up his winnings is sheer poetry. "35 elephants with all of their trappings, 4000 white stallions, and 25 tigers--" "That's not so bad--" "Oh, and the Sacred Tooth of the Buddha--" "Oh, that was a gift from Marco!" "...and all the commerce from Burma for one year." It's a great scene, and it sets up what seems to be the resolution of the story as the Doctor wagers it all against the TARDIS.
But in an episode that's absolutely jam-packed, that's nowhere near the end. The Doctor loses, Tegana plays Marco Polo's eagerness to leave the Khan's service against him by suggesting that Marco's sympathies secretly lie with the TARDIS crew, and Ian is set to go on trial for the theft of the Khan's property. Again, this scene works well because Nesbitt plays it well...but it also works well because the script plays him as a man with an intimate understanding of people's weaknesses. Tegana knows what secrets Marco holds, and he knows that revealing them to Kublai Khan before Marco has the chance will leave him on the defensive. It's actually a very well-written as well as a very well-acted sequence.
Unfortunately, the resolution starts to feel a bit perfunctory here. The death of Ping-Cho's intended, while a sequence that is not without a certain twisted humor, wraps up her sub-plot with the rapidity of a Restoration comedy deus-ex-machina. The TARDIS crew's realization of Tegana's plan, and their escape to the throne room, is equally rushed. And in the end, all they really do is tell Marco what's going on and let him do all the heroic lifting. It works better than it should, because at this point Marco has been on the show long enough to feel like a protagonist in his own right, but it's still a little odd in a show called 'Doctor Who' that the final confrontation features two incidental characters slugging it out.
And then there's the final conclusion, which has none of the elegance of the novelized version. Instead of Kublai Khan graciously ceding the TARDIS to the Doctor as repayment for saving his life, Marco just sort of shoves the keys their way and they sprint for the hills. And Kublai Khan, who had been established pretty well as someone who was more than just a figure of comedy, who had the power of life and death over Marco and was shown to distrust him because Marco seemed to have a conflict in loyalties over the TARDIS and its crew, just shrugs the loss of the magical caravan off with a joke about backgammon. It's a weak ending to a good episode, and it makes you glad that Lucarotti had a second chance. Because with two opportunities, he made a story that's a genuine classic.