This story, as do most of Munro's, focuses on how people interact, what part of their inner self they compromise or embellish in order to deal with life and the people in it. There is usually, as is here, a conflict that unravels slowly through character revelation and interaction, specifically dialogue and reflections, and a resolution that often leaves the character changed only in their acceptance of a situation.
Here, we have a smoldering fight and unhappiness after a year of marriage when realities about one's partner sink in and are often resented. Munro shows us both sides of the situation and we find that they do love each other but that the veneer has worn off. We find the battle one of self-identity and change forced by becoming a partnership. As the ice thaws, one makes the effort to break through and the other accepts, but first considering choices that prepare for future scenarios.
But Munro's ending to this story has just a bit of dissatisfaction to it–not because of the ultimate changes made, the growth in the relationship–but rather the impetus and how it was handled. As they all drive home, and some peace is made, suddenly out of the dark a car comes straight at them, veering off into the cornfields just before they would otherwise impact. They drive the short distance home and sit in the car in the driveway, likely stunned by the moment that could have ended their lives.
What spoiled it for me? Well I just don't buy that they didn't stop and check on the driver and passenger in the other car. This wouldn't seem realistic, especially since they live out in the country where other cars are not likely to be going by in any number. This sort of changed the image of the two characters that Munro so carefully built.