I knew it was her from half a block away. When my old friend moved through the crowd, I saw that she had her phone pressed to her ear, and I felt a familiar tug of loss. She and I used to talk to each other all the time — from our apartments and our tiny desks at our starter jobs, on noisy streets at moments just like this. More than a decade had passed since those days, and I had no idea who’d taken my place on the other end of the telephone line. “Hello!” we cried out, and exchanged big-hearted waves. Neither of us stopped walking.

We had met in high school in New York City and remained close during college, sending letters to each other’s dorms and, over breaks, reuniting over dim sum on Pell Street or trawling the racks of Canal Jeans. When we returned home after graduation, we made a two-headed unit, speaking in a language of arcane in-jokes and serving as each other’s de facto plus-ones. We took our mothers on double dates, trotted out our romantic interests for each other’s scrutiny, went on vacation together.

It was on one of our phone calls that our friendship came to its end — though it took me a few weeks to understand that she was gone. We were chatting on our way to work when she told me she had to take another call and she’d ring me right back. And then she vanished. I left voice mail messages and texts. I lamented to our mutual friends. I felt abandoned and bewildered.

Perhaps she offered no explanation because she had none. That she was no longer in the mood should have been reason enough.