We’ve taken well over two thousand photographs of our daughter Lucy and she is only nine months old. Sometimes I lose myself for hours in browsing through those photos after Lucy has gone to bed, and when I resurface I always ask myself what I’ve been looking for. After all, she’s just a few steps or a fitful cry away. But I’ve just been highjacked by seven photos of another baby and they’ve sent my thoughts into a tailspin. I had ordered prints from an online photo processor, but what arrives is a small stack of someone else’s photos—images of a couple and their brand new baby.

I seize on the photos with an avidity that surprises me. In the first one, the new mama wears an expression of exhausted contentment, the baby’s head nestled on her shoulder. There is a bandaid on her right wrist and it makes me wonder how her labor went. Both the mama and the baby look healthy, though, and the rest of the photos are from the couples’ home. Is the baby a girl or boy? The next photo, a changing-table shot, puts that question definitively to rest: a boy, circumcised. He has a scrim of hair, enormous ears, a broad face like his papa. He must be at least a week old in that photo because his belly button looks quite official. I’m ambushed by sourceless affection for these strangers. I actually find myself counting the baby’s fingers and toes, something I hadn’t done when Lucy was born.

Like a detective I scrutinize the evidence casually arrayed in the misdirected photos. How much can I discover about them? The couple is older, maybe mid-40s. This must be their first child because there are no shots of siblings holding the new arrival. In fact, there are no other people and no photos of the two parents together, and I imagine them alone in a cozy house somewhere, taking turns with the baby and the camera. Are they from Wisconsin, as his tee shirt proclaims? Their sunburned noses suggest they live somewhere sunny or have just returned from their last vacation as a childless couple. He wears glasses, I think to myself as I peer at the indentations on the sides of his nose, and my obsessive acumen is vindicated by the next photo which depicts the glasses themselves lying on the couch next to the baby. They clearly had a baby shower, as the gift boxes of Gap clothing attest, and I bet they knew they were having a boy since most of the outfits are variations on the theme of blue.

Another photo shows the papa and the baby sound asleep on their sides, facing each other, one big and one little arm outstretched, their hands clasped. My partner Jay took a nearly identical photo of Lucy and me in the first few days of her life and that image has become my dad and my partner’s favorite. I’ve never really liked what I consider its cloying sentimentality, but now, gazing at someone else in that same posture, I think proudly to myself, “He is going to be an exceptional father.”

But it is the last picture which most arrests me. It shows the baby awake and peering blearily at the camera, wearing the exact sleep sack that my daughter wore in her first week. I am jolted by the familiarity of the image. I don’t know this baby, but I know something about how it must have felt for his parents to take that photograph. When Lucy was born, Jay and I had a blessed two-week bubble of time to ourselves before he went back to work and our families began to arrive. With no distractions and nothing to do, we simply lay in bed and stared at our daughter, wholly absorbed in her presence, our world telescoped down to the size of her tiny body. I’d heard new parents describe the wonder they felt for their newborns, but when it happened to us I realized that “wonder” was shorthand for a much larger emotion that couldn’t be put into words but that was understood by parents everywhere. We’d been inducted into a club where you could say something like “wonder” and initiates would nod knowingly and remember their own first weeks with their newborns, while outsiders would hear only the tinniest echo of the word’s meaning. Now I am a veteran of the club, holding photos that depict two new inductees as they experience “wonder” in its most expansive sense. I know their bubble of time will end soon and it will only take a few short months before, like us, they become old hands at parenthood who feel nostalgia for the days when their son was “little.”

Gradually I begin to understand my obsession with the new family. I think I enjoy looking at the other family’s photos because they are fresh to me. Scrutinizing them allows me to enter the memory of Lucy’s first days from a new portal and to be surprised by what I remember, rather than revisiting the same familiar touchstones. I like these strange photos not for what they depict but for how they make me feel: the violence of my love for my own baby girl.

I do my fair share of misty-eyed gazing at my sleeping child, but I am not generally a sentimentalist. For me, motherhood is most intense when it hurts. I most feel like a mother when I’m hit in the solar plexus with nostalgia, when something jolts me into remembering Lucy when she was new and I am blindsided by the disparity between the newborn Lucy and her present self. Or when I feel vertigo at the thought of what I could lose—not Lucy herself (that fear is too submerged to be articulated), but my memories of her, how I’ve steadily accreted my knowledge of her. I’ll always remember that we called her Piglet and Thunderpants for the first few months, but will I always be able to hear in my mind’s ear the sounds that prompted those names? Will I always be able to animate each successive manifestation of Lucyness that has been astounding us for nine months? That the answer just might be “no” provides a recurrent pinprick of pain in my sense of myself, like a needle sewing me ever more tightly to her.

As I writer, I’ve been trying to catch my daughter in a net of words since before she was born. I began writing letters to her as soon as I could feel her roiling in my belly. I keep a daily journal, my chicken scratch a serge stitch to stop the unraveling of time under my fingertips. I write longer essays in her baby book to give permanence and heft to her milestones. But my words only seem to hover near her, vaguely approximating her shape in the air, never truly capturing her, and so I’ve also turned to photography.

My photographs do a better job of capturing Lucy, in part because they aren’t inventions of my mind. They enthrall me and keep me up late at night because, unlike my writing, I can discover new things about Lucy in them. Yet I have to be gentle with them. I am afraid that if I revisit them too often, they will deaden. I’m scared that my memory will shrink to fit only what I’ve documented. At last, I get it. I can look at the photos of the new family with the absorption that I can’t quite permit myself with my own photos of Lucy. I can feel for this family the unalloyed, sentimental wonder that I haven’t felt for Lucy since those first few weeks because I need not be scared that I will lose them in the slow dissolve of memory.

I show Lucy the pictures of the newborn boy and, as she does when she sees pictures of herself, she screeches and flaps her arms like she is attempting flight. I’ll think about this little boy every time I look at Lucy’s baby book, where I’ve pasted his photos. His story belongs to Lucy’s story now—he has become a small part of my memory of Lucy as a baby—and someday I’ll tell her about this gnomic emissary from an unknown world who arrived in our mailbox wearing her clothes and made me love her even more ferociously.

Amy Reading has just finished graduate school and this is her first nonacademic publication. She lives and writes in upstate New York with her partner, daughter, and a baby on the way.