So it came to pass that I started logging on to Facebook. And, like seemingly everyone else I’d ever met, eventually S “friended” me. My policy has been always to accept whoever asks, no question, and never to friend anyone myself. (In this way I maintain the fiction that I’m not an active user.) I glanced at S’s picture—that pretty smile and Bonnie Fuller shag—clicked “confirm,” and unconsciously relegated her to the vast, benign category of “friends” with whom I never interact, but who constitute a comforting background chorus.

S would accept no such fate. Straightaway, photos of her nightlife dominated my news feed. Her status updates were bubbly shrieks of uppercase letters and exclamation points. I considered “hiding” her—this is the function that allows you to make a friend invisible without going so far as to “defriend” her—but that seemed excessive. S was, after all, my envoy to an alternate universe of abandon. Twenty-five years old and barelegged in winter was a variety of fun I’d never known before.

Then, in the spring, a man—G—entered the frame. At first he appeared with other men, the whole group at a table in a bar, offering pints of beer to the camera. But quickly everyone else fell away and he emerged in photographs with S alone, his arm thrown around her. At first the gesture was friendly and drunk, but over time I could track the way his arm both relaxed and tightened, his hand cupping her shoulder, and see him taking possession.

It turned out that G lived in London, and in the fall S posted images from a visit: the couple in a crowded pub, or on a bridge at sunset. By now I habitually clicked through S’s photo albums, a diversion far better than popping into a colleague’s office for a romantic update. Here, I had the satisfaction of a love plot unfolding right in my living room, complete with revolving backdrops and the suspense inherent in a long-distance relationship. When was her next trip? Oh look, G is coming to town! At this I felt relief: I took it as evidence that he was as committed to her as she was to him.

But that was nothing compared to my delight the December morning I logged on to Facebook and was greeted by a photo of S and G grinning madly on an enormous gray sofa, S presenting the back of her hand to the camera to show off the diamond on her finger. I have never known that kind of happiness with a man. Without thinking, I started to type a note of congratulations into the comment box, but midway through I erased it and logged off. I hardly knew this person. When had I become such a voyeur?

Still, I continued to devour her fairy tale. Here G was introducing her to his parents; here she was introducing him to hers. A year had passed since S had friended me. We never exchanged messages, or commented on one another’s postings, or saw each other in person (save for one early, awkward encounter in a furniture store, during which it took me a moment to place who she was). Yet I thought about her often, even when I wasn’t on Facebook, as I would any close friend in a similar joyful circumstance. More, in fact: her news thrummed inside my chest as if it were my own. I wondered where the wedding might take place, what she would wear. Being a voyeur isn’t so bad, I decided, as long as you’ve been invited—and you don’t tell anyone.