Ann:
Since we're reading this together, I will share with you and the other members of the Klub that author's use a "trick" also called "hanging a lantern," which comes from the old Silent Movie days when a piece of the scenery stuck out illogically, they'd shout "Hang a lantern on it and nobody'll notice it."
Sometimes authors need to do this to prevent spilling the beans. I do it in The Jade Owl when Nick and Rowden first enter the tomb and there's light. Now in an earlier version I had a long explanation for the light, but because of that explanation when Wu Tze-t'ien appears and is alive, the surpirse was gone - no shock, because everyone has figured out that "someone" kept the lights going. I replaced all that by having an unexplained "light" in the red chamber which remained unexplained. So when we see the lights in the tomb, Rowden hangs a lantern on it, by saying that these were similar to the unexplained light in the Red Chamber "and he never got a satisfactory explanation for that either." THEN I LEAVE IT ALONE. And no one notices it or questions it, and thus the Empress Wu's appearance is a surprise.
This reminds me of a comment made by Sean Astin on a commentary for The Two Towers, when he asked the lighting director in the Cireth Ungol scene about some unexplained lighting: "Where is the light coming from?," Astin asked. The man smiled and said, "the same place that the music comes from."
My favorite logic slip comes, of course, from Gilbert & Sullivan. The Pirates of Penzance. Act One is set on a Summer day in Cornwall on the heroes 21st birthday. Major-General Stanley's daughters are skipping along the coast, splashing in the water and having a picnic. Of course we learn in Act Two that the hero was born in leap year on the 29th of Febraury (a plot inequity to nullify his piratical contract). No one ever questions that bright Summer day picnicking in Cornwall in Act One that actually takes place in the dead of winter.

In this case Gilbert didn't hang a lantern on it. He just presents the fact out of sequence and the audiences misses the logical slip. Oh, there's all sorts of slips made on purpose. I could write a book. (Wait a second, I think I did).

Ed P