Robert Holmes creates such an interesting character in Li H'sen Chang. Until we meet Weng-Chiang (if that is his real name), Chang serves as the main villain of this story, but in reality, he is a pitiable creature. His master, Weng-Chiang, is never happy with him or his actions. Chang does his best to find young women, full of fire, to serve Weng-Chiang's cause, but none of the ladies he finds seem to suit Weng-Chiang's purposes.
Chang is constantly demeaned, ignored, and insulted by his master, and yet his desire to serve keeps him coming back to Weng-Chiang's lair to try and make it up to him. Chiang's motives aren't borne of malice to inflict harm on the young women he finds, or to murder those who he might deem dangerous or incompetent. He is merely following the orders that he has been given, no matter how questionable they are. As this story goes along, you almost hope that Weng-Chiang, a talented showman, will see the errors of his ways and throw off the yoke of his Chinese god, because he really deserves better.
I could talk about the rat, but it really is the flaw in the Persian rug in a story that is just so blissful to watch half way through that it really deserves to be longer than six parts.