At the end of Gates of Babylon, The, I was pretty well convinced that author Michael Wallace had come to hate his characters. After all, he had put Jacob Christianson and the rest of the Blister Creek residents into a world where a supervolcano eruption on the other side of the planet had quite literally created World War III due to crop failure, etc.
Midway through Hell's Fortress, I realized that wasn't it at all. He was presenting a clear picture of how the polygamist cult in which he was brought up would be viewed by the world in the event of catastrophe ... and it's not always pretty. Starving refugees start showing up at Blister Creek because they have been told that there is two years' worth of food there -- and there is.
Jacob, the extremely reluctant "prophet" of the group tries to reason with the refugees, even giving them some food in exchange for taking his sister, Eliza, and two others out of the valley. Eliza is trying to fid her FBI agent fiancé, Steve, who had gone to Los Angeles the previous year and disappeared. Instead, the refugees abduct four members of Blister Creek, steal their supplies to add to those given, and dump them in the middle of the desert.
The mistake they make here is that Sister Miriam was once FBI agent Haley Kite ... and she's pretty good at what she does. Including killing people.
So, we have the simultaneous plot lines of Eliza, Miriam, et al., trying to get to Los Angeles while Jacob tries to balance being the "prophet" (he is not a believer) with being a physician who wants to help people.
I think Wallace may have his head back in the game on this one.