The story is told in the present but is Lilly's memory of the trip. The author reminds the reader every once in a while that Lilly is remembering the deep past, "she thinks now," and "it amazes Lilly now..." At one point, the landscape becomes a graphic image of the story's history, "Lilly kept looking out at the valley, then turning and looking back up at the Beartooths. How could any traveler decide which to choose?" Then they drive down into the valley.
The theme is detailed in this sentence, "In a way, it could almost be seen as comforting, to realize that as the fabric and surface of a life begins to fray and disintegrate, and a traveler finds him-or herself in freewill, that there exists beneath the firmament of our relative unawareness the logic and order that is far more connected and interlocked." I find this much more comforting than any sort of religion. Also, another theme can be made here. "Of believing he was free to keep on going." Aren't we all fooled that we can always and forever keep on going, until we aren't.
At two points in the story, Lilly and her father are confronted with a drunken woman who is obviously at rock-bottom much as Lilly's father must have been, totally down and out and dependent on the kindness of strangers.
We see Lilly growing as a person while on this trip with her father yet he never lectures her and actually, he never speaks. Lilly shows empathy when she imagines and wonders what it would be like to be the old man who is living in a trailer about to fall over. "What would it be like, to be him--the man in the stained T-shirt, porch-staggered and blinking groggily at the bright sunlight? It was only her own victory of being loved deeply that allowed her the luxury of such indulgent imaginings, such frightful considerations of slumber, detachment, escape"
I've only touched on a couple of things in this richly detailed story. I highly recommend reading it. You can buy a copy of the Idaho Review here at this link. It's a good life lesson as well, "How dare anyone sleep through even a moment of it?" Get busy living or get busy dying, something like that from Shawshank Redemption.