A woman opened the door.

She was wearing a red dress. Her hair was dark, shoulder-length, slightly wavy. She was slim, medium height. She smiled when she saw him. He put his hand on her face and she kissed him — not a greeting kiss, not a peck — and something in my chest cracked cleanly in two like a piece of sea-glass.

I took photos. My hands were shaking so badly that the first three were blurred, and I remember thinking, with some distant and still-functioning part of my brain, that I needed to steady my elbows against the steering wheel. Evidence, I thought. You need evidence.

Then I noticed the mailbox.

It was a simple black mailbox, the kind you find at every hardware store, fixed to the porch railing. There was a name on it in white stick-on letters: CALLOWAY.

Calloway was my maiden name.

I sat with that for a moment. My first thought was coincidence — it’s not an uncommon name, there are Calloways all over this city, Calloways in the phone book, Calloways who have nothing to do with me or with Marcus or with any of this. But even as I constructed that thought I was looking at the woman again through the windshield, through the long rectangle of the open doorway, and something about her was pulling at me, tugging at the hem of my attention the way a child tugs at a sleeve.

Her hair. The way she stood. The tilt of her head when she laughed.

I drove home. I went directly to the shelf in the living room where we keep the photo albums — we are one of the few couples left who still print photographs; Marcus had always insisted on it, said there was something important about holding a memory in your hands — and I pulled out our wedding album and sat down on the floor and opened it.

There is a photo near the middle of the album, page fourteen, that I have always been fond of without entirely knowing why. It’s not a formal shot. It was taken by my aunt during the cocktail hour — one of those candid moments that a photographer misses and a relative with a disposable camera catches. In it, Marcus is laughing at something someone has said. And beside him, half-turned away from the camera, is a woman in an ivory dress.

I had always assumed it was me. Same hair. Same build. She’s slightly blurred, caught mid-turn, her face not quite visible. I had seen this photo dozens of times and each time filed it away without examination, the way you file away anything familiar.

I looked at it now — really looked at it — and understood that the woman in the photo was my twin sister.

My twin sister who had died fourteen years ago.

Or who I had been told had died.

Her name was Clara. We were not identical — fraternal twins, the doctor had always said, though people who knew us both thought we looked more alike than the word fraternal implied. Same dark hair, same build, same small scar near the left collarbone from a fall off a bicycle when we were seven years old. We finished each other’s sentences. We had the same laugh. We could not, as children, bear to be in different rooms.

When I was twenty-three, Clara was in a car accident on the interstate near our hometown. The car was totaled. I had identified her — or what I was told was her — at the hospital. The casket had been closed. My mother had said it was better that way. I had worn black for a year and built my grief into a monument inside myself, something I walked around every day without walking through.