Like the fact that Erin O'Connor moved into the apartment across the street in March 2015 and has not smiled once.

She is twenty-six, Irish descent, works as a data analyst for some company in Manhattan. She comes to my store every evening at six-thirty, always the same items: one can of tuna, one loaf of bread, one banana, sometimes a bag of apples. She pays in cash. She says thank you in a voice that sounds like it belongs to someone else.

On a Tuesday in April, she came in with a cardboard box. The box was leaking. I could see blood on the bottom through the gaps in the cardboard. She set it on the counter between the cigarettes and the lottery tickets and said, "Can you help me?"

I looked at the box. I looked at her. I reached under the counter and pulled out a roll of paper towels. I put them on the counter between the cigarettes and the lottery tickets.

"You should take it to an animal shelter," I said.

"I can't," she said. "They'll kill it."

"Who will?"

She did not answer. She picked up the paper towels and the banana and the tuna and the bread and the apples and left. I watched her cross the street and go into her apartment. I watched her door close.

The box was still leaking on my counter. I wiped it up with more paper towels and threw them in the trash.

Three days later, she came in at six-thirty and bought the same things. This time she said, "Thank you" in her own voice. It sounded different. Not happier. Just more real.

I did not ask about the box. I did not ask about anything. In thirty years, I have learned that people do not need you to ask. They need you to be there when they are ready to talk.

The box stopped leaking after a week. I know this because I started noticing things. Not because I wanted to. Because I am fifty-eight years old and I have nothing else to do but notice things on a street where nothing happens.

Erin started coming to the store more often. Not for groceries. Just to stand there, talking about the weather or the price of eggs or nothing at all. She would stand by the counter and talk while I rang up her items, and her voice would get stronger each time, like a muscle that had been atrophying and was slowly learning to work again.

I noticed other things too. The way she started leaving food on the doorstep of Mrs. Chen next door. The way she began saying hello to Mr. Williams on the stairs. The way she started smiling—not often, not broadly, but sometimes, when she thought no one was looking.

I noticed because I notice things. It is what I do.

The fox grew. I know this because one evening Erin came into the store with a dog leash in her hand, and I knew immediately that whatever was in that apartment was no longer small.

"Is that for a dog?" I asked.

She looked at the leash. She looked at me. "No," she said. "It's not a dog."

"What is it?"

She did not answer. She bought her tuna and her bread and her banana and left. I watched her cross the street. I watched her door close.

The gentrification started that summer. New buildings went up on the blocks I had never cared about. New coffee shops replaced the laundromat where I used to wait for my coffee to dry. New people moved in—young people with expensive shoes and expensive opinions and expensive voices that sounded nothing like the voices on this street for the last thirty years.

Rent went up. People left. Mrs. Chen moved to Queens. Mr. Williams moved to Brooklyn. The people I had known for thirty years were disappearing, one apartment at a time.

Erin was next. I knew it before she did. I could see it in the way she packed boxes in the evening, the way she stopped coming to the store, the way her voice on the few times she did come sounded like it belonged to someone who was already gone.

On her last day, she came to the store at four in the afternoon, which was unusual. The store does not get many customers at four. She carried a manila envelope and set it on the counter.

"Hassan," she said. "I'm moving."

I nodded. "I know."

"I wanted to give you this."

She pushed the envelope across the counter. I opened it. It was the ledger. The store's ledger. Thirty years of sales and purchases and debts and credits, written in my own hand in my own shaky script. But it was not just numbers.

Between the entries, in Erin's neat analytical handwriting, were notes. Notes about every customer on this street. Names. Preferences. Stories. Mrs. Chen's husband died in 2008 and she still buys two cups of tea every morning because she cannot bear to throw away his favorite brand. Mr. Williams comes in every Thursday and buys lottery tickets he never checks because it is the only thing his son used to do with him. The young woman on the third floor who buys apples every day because her mother is sick and apples are the only thing she can eat.

Every customer. Every story. Thirty years of my observations, documented by a woman who had been here for less than a year.

On the last page, she had written: "To Hassan—you are the quietest observer on this street. Thank you for always being here."

I looked up at her. She was standing by the counter, waiting. Her face was calm. Her eyes were red.

"Why?" I asked.

"Because you noticed everything," she said. "And nobody ever noticed you noticing."

She left. I stood in the store and read the ledger. All afternoon. The sun went down. The street got dark. I kept reading.

The fox had left that morning. I know this because I was watching from the window when Erin opened her front door. The fox stood on the threshold, white against the grey morning, looking at her with eyes that were not friendly and not hostile, just present. Just alive.

Then it turned and walked down the street and disappeared into the traffic and the noise and the new buildings and the people who would never know it had ever existed.

I closed the ledger and put it on the counter behind me. I stood there for a long time. Then I locked the door and went home.

The next morning, I opened the store as usual. The sun was shining. The street was the same. The new coffee shop was still there. Mrs. Chen's apartment was empty. Mr. Williams's apartment was empty. Erin's apartment had a new family in it—a young couple with a baby and expensive shoes.

I rang up their groceries. They said thank you. I said you're welcome.

I am fifty-eight years old. I have been running this store for thirty years. I notice things.

That is all I do. That is all I have ever done.