First, please permit me to state that this is merely a confused, personal pondering session to see if I cannot figure out the fate of Glinda in Gregory Maguire's "Out of Oz." I realize that the author left it to the imagination, in some ways. That, of course, means that whatever I think happened is what happened, as there is no explanation. I should go on to say that those who have not read the book and plan on doing so should consider this entire piece a SPOILER and therefore click away. Now, I publish this not because I suffer under the delusion that anyone cares what I eked out of Glinda's last moments in "Out of Oz," but to allow whoever reads this to tell me if I missed something, their opinion or even to encourage me not to obsess over cliff-hanger endings.
I suppose I should begin my pondering with the moment in question. Gregory Maguire has Glinda in Southstairs, imprisoned for treasonous acts. There are hints that she will not be staying there long and that the sentence will only be long enough to satisfy political obligations. She is last mentioned in "Out of Oz" as resting in her prison cell when the knob on the cell door is turned. It is stated that Glinda knows who is at the door. She says aloud, "You wicked thing. You've taken your own sweet time, of course." Her use of the word "wicked" is very leading.
Now, in my mind, there are four possibilities to explain this, given later and earlier events in the series. One possibility that I have eliminated is Rain, as she was nowhere near Southstairs. Another possibility is that the Cowardly Lion has come to remove her. That seems unlikely, as he would probably send someone else. Another is that Glinda has simply lost her mind. Yet another is that Glinda is dying and imagining/seeing her best friend as she dies. The last, my favorite and what I believe is more than implied is that Elphaba has either risen from the dead or never died to begin with.
In "Wicked," Elphaba is believed to have died by the hands of Dorothy Gale. However, no one witnessed Elphaba's death. Gale saw her disappear and ran away. Nanny ran up after Dorothy ran away, somehow took control of the Elphaba situation and refused to speak a word of what she saw. Just a few pages before Glinda has this mysterious visitor in Southstairs, Nanny says that she has seen Elphaba in Kiamo Ko. Of course, Nanny is ancient and somewhat senile. There are various other mentions that Elphaba will come back, has come back or did not die at all throughout all of the novels. There may have even been a prophecy of her return, but, as always, Maguire was infuriatingly ambiguous.
Therefore, I choose to assume it was Elphaba. I also love Gregory Maguire for being a bit of a tease that drops who knows how many hints without ever coming out and saying it. Still, I would love him all the more if he just came out and said it.