This week’s story, “Under the Wave,” opens in the middle of the night, as water floods into a house. A family of three was vacationing there—a mother, father, and their son. Only the mother survives. When did you first start thinking of this scenario?

I was transfixed by the tsunami in Japan in 2011, and have spent far too much time late at night watching videos of the horror of the rising waters. I know it’s not rational, but I have had a hard time relaxing near beaches since then. In 2013, as soon as “Wave,” Sonali Deraniyagala’s brilliant and painful memoir of the 2004 tsunami in Sri Lanka came out, I read it, and it lived in the back of my mind until I read last year’s absolutely stunning “Ghosts of the Tsunami,” by Richard Lloyd Parry, about the 2011 earthquake and tsunami in Japan. Together, these narratives put pressure on my near-constant thoughts of the refugees now trying to find a place of security and peace throughout the world, and how we owe an absolute moral debt to the most vulnerable among us.

The wave is mentioned only once in the story—“The child soon learned that the woman would not look more than once at a drawing with water in it or at anything that hinted of a life lived before the wave”—and the word “tsunami” is never used. Why did you want to hold back on this kind of detail?

There wasn’t a conscious decision to hold back; I just didn’t think the character would immediately understand what was happening in all the rush and confusion. Calling it a tsunami felt too analytical until she was a little distant from the emergency, when she could piece together what happened.

The woman crosses paths with a young girl at a shelter, and the two leave together. Gradually, the girl starts to take the place of the woman’s son, denying her original identity to someone who recognizes her. Did you know from the outset that the relationship between the woman and the child would play out as it does?

I saw from the outset the allegiance of the child to the woman when faced with someone from the child’s pre-wave past—I knew there was heat and ice cream in the scene. But the rest of it came gradually.

Do you think we should see the woman’s desire to look after this child as something that springs from altruism or from selfishness?

Is altruism ever completely devoid of selfishness? Shouldn’t we be working for a world without poverty or hunger, providing all humans with excellent, free education and medical care, because it would bring all of us—our very own families and loved ones—far greater security and happiness? If we are surrounded by masses of secure, fed, well-educated people who don’t fear dying by gun violence or because they can’t afford an E.R. visit, our own quality of life and general happiness would skyrocket.

You live in Florida, a state that’s no stranger to natural emergencies. You don’t give any place names in the piece, but were you thinking of Florida when you were writing this?

There’s a very specific rental house near a beach in Florida that I put the woman and her little family into, and a very specific apartment in a northern city where she goes to live with the child in the aftermath. I have a hard time writing scenes unless I fully envision them.

You just published a collection of stories called “Florida.” Does “Under the Wave” feel like a continuation of the themes you explore in the collection?

When I’m working, I never think of my work in thematic terms, which is the terminology of literary analysis, not of creation: it’s a retrospective stance, not an active one. I can hardly see my own work at all, honestly. I write what feels urgent to me, and only in editing does my analytical brain kicks in, but even after a piece has been published I can still only see my own private vision of the piece. And it’s impossible for me to talk about my work as a whole, unless I’m parroting something someone else has told me about it. My face is pressed up against the rug, and from there I can see individual fibres, but readers are the ones who can see the over-all pattern. So I guess it’s a continuation of themes, sure, because it comes from me, but you’d be far better suited to tell me about it than I could ever be.

You’ve been travelling around the country on a book tour—does your view of Florida ever change the farther you are from it? Do you find yourself thinking of different kinds of natural calamities?

There is no place that isn’t vulnerable to calamity, particularly in the Anthropocene. The anxious brain finds the built-in flaws everywhere I go—earthquakes and mudslides and desertification galore. The truth is, where my children are at every moment feels like the most vulnerable place of all, particularly if I’m not there. And my vision of Florida is just that—my own idiosyncratic vision probably unshared by anyone else who knows the place—and it doesn’t change with distance.