The 24-hour diner is dead. Long live the 24-hour diner. | Mike Newall

The midnight waitress works by a simple motto: Come in rested and ready.

It’s a credo that has carried Linda Harris through 27 years at the Mayfair Diner, every one of them spent on the overnight shift. As soon as she arrives (early, at 10:30 p.m.), the midnight waitress fills the ice creams. Readies the puddings. Makes sure the breads are sliced and the soup ladle ready.

Because in the early hours at the Mayfair, you never know what’s going to happen.

The pleasantly intoxicated could stagger in — or the streakers who sometimes bolt from the bathroom on a booze-fueled dare. The counter could fill with the quiet nighthawks who show Linda photos of their dogs. Or the hours could pass slowly, with Linda puttering and cleaning to pass the time. Or, she could be ping-ponging between eight or nine booths, never forgetting the little things — the toast, the sides, the little cup of honey mustard.

“The little things are what make the most importance,” Linda said one recent icy night, as the clock above the Mayfair’s multicolored tiled counter neared midnight.

In recent months, one could be forgiven for thinking the end of the 24-hour diner had come to Philadelphia — what with the iconic Oregon and Penrose Diners shortening their overnight hours. Two Midtown diners and the late, great Little Pete’s are already gone.

Though plates will no longer clatter through most of the wee hours in South Philly’s deepest recesses, the 24-hour diner is still for now very much alive in Philadelphia. Nestled downtown is the last of the Midtowns, and the South Street Diner. Farther north, there’s Linda’s beloved Mayfair, and stretching south, the Broad Street and the Melrose, all owned by the city’s diner dynasty: the Petrogiannis family.

Yes, staffing is a challenge, and UberEats stings, said Manoli Lagoudakis, who manages the Mayfair, and whose uncle Michael Petrogiannis owns the empire.

“But we’re still going strong,” he said of his spot.

What was really lamented when word came that the Oregon and Penrose would close at a reasonable hour was the loss of the particular aura of a diner at night. The liminal, dreamlike landscape of a Formica counter at 2 a.m. The sense that, once you pass into that neon glare, you are no longer in the world at all.

A late-night diner is a place where secrets are kept. The staff has a motto at the Broad Street Diner, too: Whatever happens on third shift stays on third shift, said waitress Donna Miller.

It’s a place, too, where the waitresses call each other family. “We stick up for each other and defend each other,” said manager Amy Rockelman. And they console each other: Like on a recent Thursday, when Donna began crying. She keeps a photo taped to the inside of her order book — of her son, Johnny, who took his own life 18 years ago. It’s still a daily struggle, and the women know that. That Thursday, Amy took Donna into the kitchen, held her and prayed by the waffle-maker.

A late-night diner is a place where you can get a little philosophical over the pancakes. Like at the South Street Diner, full to bursting on a recent Sunday morning, when Eric Mattson, 29, and Kristan Pagliei, 24, sat in a corner booth, on what didn’t start as a date but was rapidly moving toward one.

“He’s a poet,” Kristan told me.

“I don’t know, maybe,” said Eric, who by day works construction. “What does that even mean?”

A late-night diner is a place where some pay the bills in between dreams. Like Jessica Sessions, a 29-year-old waitress at the South Street Diner who was working one of her last shifts before shipping off to boot camp. The mother of three hopes to own her own restaurant, with all-day service, and a big outdoor patio. She thinks a soldier’s life, and the benefits that come with it, might help her save enough. “I’m not going to get there doing this,” she said.

And a diner is a place that, for some people, becomes the dream.

All these nights, for nearly a third of a century, have made Linda Harris happier. Before the divorce that led her to seek the job in the first place, she was scared of the world. On the midnight shift, she learned to really like people.

Her daughters, 11 and 15 when she started, learned that their mother would always be there for them. But to do that, she just had to be at the diner while they slept. And Linda learned that the police officers who visited the Mayfair were fond enough of the place and the people who worked there to drive past her house in the dead of night to make sure her girls were safe.

She learned to laugh with the drunks, to indulge the old-time regulars — so many of whom have passed — and even the kids who she wishes would show her a little more respect these days.

“You’ll go to a table, and they’ll go, ‘Well, thanks, Hon.’ I’m not nobody’s Hon.”

Linda turns 70 soon. She has a job at the Mayfair as long as she wants to work, her boss recently told her. And she’s not going anywhere.

“I have a very big fondness of being here,” she said. “Someone asks me where I work, I’ll tell them I’m a server at the Mayfair Diner, and I’m very proud to say that.”

Before the end of her midnight shift, she makes sure all her tables are clean and everything is stocked to her satisfaction. That coffee is ready for the new shift. That the sinks, the soda machine and milkshake mixers are shining. And then she goes home, and has her tea, and plays with the dogs, and the midnight waitress sleeps.