the characters confront themselves and each other. They change. Some force is changing them. Is it evolution? Progress? Is it good or bad? Or indifferent? We see how each individual handles what is happening to them, all differently.
Lena confronts her "self" at the end. Her husband doesn't even make it out. But she accepts this "new" husband. And she is different. How is she different? Why does she accept this man? Why did she make it out but her husband didn't? They have both been changed by the experience in the Shimmer. Are they evolved? Better?
In the flashbacks we see they are happy together, but they sabotaged that happiness (again, the self-destruction): she cheated on her husband, her husband would leave her for long periods of time to take on dangerous work. Their lives were not perfect.
No answers, really. But raises questions.