It happens in the way that most important things end up having happened for her: accidentally, and because she does something she is not supposed to do. And it happens in the fashion of many happenstantial occurrences, the result of completely plausible decision making, a little diversion from the norm that will, in hindsight, seem almost too coincidental: a slight veer and suddenly everything’s free-falling, the universe gleefully seizing that seldom chosen Other Option, running, arms outstretched, like a deranged person trying to clear the aisles in a grocery store, which is, as a matter of fact, where she is, the gourmet place two towns over, picking up some last-­minute items for a dinner party for her husband, who is turning sixty today.

This one is a small act of misbehavior by any standards, an innocuous Other Option as far as they go: choosing a grocery store that is not her usual grocery store because her usual grocery store is out of crabmeat.

Afterward she will remember having the thought—leaving the first grocery empty-handed—that such a benign change to her routine could lead to something disastrous, something that’s not supposed to happen. This is how Mark—­scientific, marvelously anxious—­has always looked at the world, as a series of choices made or not and the intricate mathematical repercussions thereof. Julia’s own brain didn’t start working this way until she’d known him for a substantial period of time; prior to that she’d always been content with the notion that making one decision closed the door on another, that there was no grand order to the universe, that nothing really mattered that much one way or another; this glaring difference in character is perhaps what accounts for the fact that Mark dutifully pursued a graduate degree in engineering while Julia neglected to collect her English and Rhetoric diploma from Kansas State.

Now, though, they’ve been together for nearly three decades and so she did consider—­just a fleeting thought—that so cavalierly altering routine could result in some kind of dark fallout, but at the time she’d been envisioning something cinematically terrible, something she wouldn’t have encountered had she just forgone the crab instead of driving fifteen minutes west, a cruel run-­in with a freight train or a land mine, not with an eighty-­year-­old woman assessing a tower of kumquats.