A man fell on the subway today. I was watching people slip through the metal doors connecting our car to the next, this door then that door sliding open, and shut, bouncing on the mechanism, open, and shut, when a woman said, “Oh…”

Everyone turned to see him sprawled across the gap between our train and the platform, half onboard and half not. I had the sickly momentary thought that he might fall through. We all had this thought. We all braced to witness the tragedy of this poor nondescript in his faded black business suit. In the wildness of his spasms above the gap, he reminded me of a spider twitching in a drain. I wanted to look away. He would be drowned any moment — lost to the rat-strewn sub-train world, whose courses to me are as obscure, and as obliviating, as the inner sluices of sink-pipes sluicing on.

The man caught himself. His elbow found purchase on the concrete platform. We watched as he turned onto his stomach, gingerly, as one turns beneath sheets, not wanting to dislodge them. He brought one knee forward, then the other. And stood. A couple men had gotten up to help him. He waved them back and began to brush the dust from his slacks.

Businessman, balding, early fifties — as unremarkable a schmoe as any. He didn’t seem to be in pain. He didn’t curse. He didn’t blush. He made no effort at levity, or sarcasm. Said nothing as he shouldered his bag and stepped forward. Still, there was something heavy and apologetic about the way he stared at the ground gathering his wits.

“Are you OK?” A woman sitting opposite the doors.

The man shut his eyes and nodded vigorously.

“What happened?” she asked. Even in the greenish fluorescent light, the woman looked urbane, accomplished, concerned. She might have been in her early forties. Her off-white blouse was crisp and tailored. Her nubuck shoes had gold-tipped laces.

“Just slipped.” He shrugged and looked at a cruddy black streak on the floor, the mark his heel had left as it slid beneath him. “Graceful ,” he muttered.

“It wakes you up!” the woman trilled. The conductor was announcing that the doors were closing, and the man didn’t hear. “Wakes you up!” she said again. “A shot of adrenaline!”

A few more people rushed on.

“Better to do it in front of strangers,” another man said. Someone chortled. A general murmur of assent. “That way you can change the narrative.” This man was wearing Buddy Holly frames and a tight forest-green sweater. His friend launched into a narrative about falling in the park, and everyone went back to their books and smartphones.

I stared at the black skid mark his heel had left on the floor. In about five minutes, I thought, these doors will open and this car will empty, and a new group will walk on — another cast gathered for another minor tragedy, the trillionth iteration of this ritual. In five minutes, and until the end of time, nobody will notice this black streak. Nobody will know what it means. I thought of similar markings on concrete highway dividers, of tire marks veering nonsensically into the shoulder.

My mother taught me a game when I was five. With a pencil she drew two lines, a start and a finish, and two dots on the starting line. It was a race: my dot against hers. She fixed the pencil’s tip on her dot and held it in place by pushing her finger against the eraser. She showed me how to push down, and down, and carefully — forward. The graphite tip skimmed up the page, leaving a trail like a comet. She marked the very last trace of the line with another dot and fixed the pencil’s tip again. Whoever crossed the finish line in fewer moves won.

So I’d seen this mark before. The first slip of many slips all the way to the end.

It was a simple record of that panicked half-second, the insufficient friction-coefficient, the collision of suit and skeleton and cement, and yes, why not, the sudden pounding surge of adrenaline. All of it was there, smeared in coal crayon across the floor.

“I love your shoes.” Someone complimenting Ms. Adrenaline on her nubuck loafers. The train slowed, pulling into Grand Central.

“First day wearing them!” She was breathless. Everyone turned to admire.

“Well, aren’t you glad I said something!”

“Yes! If you get compliments the first day, then you know you’re onto something!”

Et cetera.

I looked at the man who fell. He, too, was looking at the shoes. I wondered, with him, whether anyone remembered his fall at all. I wondered, with him, what kind of material the subway floor was made of, that it would support these gilt shoes, yet send his sensible rubber heel skidding. Some kind of slick poly-something, no doubt, made to resist chewing gum, made to be soiled, then cleaned, then soiled again. Anyway, plastic.

Better to fall in front of strangers. That way you can change the narrative. The only narrative worth remembering here, the man must have thought, limping toward the terminal, aching in places he’d never ached, is that aging, like any calamity, happens in moments. From that moment on, he’d be walking more slowly. He’d be walking like a man in his fifties.

I rode the train, restive, back to Times Square.