All the guy was doing was slicing inch-thick pieces of bread, putting them in a toaster, and spreading stuff on them. But what made me stare — blinking to attention in the middle of a workday morning as I waited in line at an unfamiliar café — was the way he did it. He had the solemn intensity of a Ping-Pong player who keeps his game very close to the table: knees slightly bent, wrist flicking the butter knife back and forth, eyes suggesting a kind of flow state.

The coffee shop, called the Red Door, was a spare little operation in downtown San Francisco. There were just three employees working behind the counter: one making coffee, one taking orders, and the soulful guy making toast. In front of him, laid out in a neat row, were a few long Pullman loaves — the boxy Wonder Bread shape, like a train car, but recognizably handmade and freshly baked. And on the brief menu, toast was a stand-alone item — at $3 per slice.

It took me just a few seconds to digest what this meant: that toast, like the cupcake and the dill pickle before it, had been elevated to the artisanal plane. So I ordered some. It was pretty good. It tasted just like toast, but better.

A couple of weeks later I was at a place called Acre Coffee in Petaluma, north of San Francisco. Half of the shop's food menu fell under the heading "Toast Bar." Not long after that I went to The Mill, a big, light-filled café and bakery in the city. A small chalkboard listed the day's toast menu. Everywhere the offerings were more or less the same: thick slices of good bread, square-shaped, topped with things like small-batch almond butter or apricot marmalade or sea salt.

Back at the Red Door one day, I asked the manager what was going on. Why all the toast? "Tip of the hipster spear," he said.

I had two reactions to this: First, of course, I rolled my eyes. How silly; how twee; how perfectly San Francisco, this toast. And second, despite myself, I felt a little thrill of discovery. How many weeks would it be, I wondered, before artisanal toast made it to Brooklyn, or Chicago, or Los Angeles? How long before an article appears in Slate telling people all across America that they're making toast all wrong? How long before the backlash sets in? For whatever reason, I felt compelled to go looking for the origins of the fancy toast trend.

If the discoveryof artisanal toast had made me roll my eyes, it soon made other people in San Francisco downright indignant. I spent the early part of my search following the footsteps of a very low-stakes mob. "$4 Toast: Why the Tech Industry Is Ruining San Francisco" ran the headline of an August article on a local technology news site called VentureBeat. For a few weeks $4 toast became a rallying cry in the city's media — an instant parable and parody of the shallow, expensive new San Francisco.

The butt of all this criticism appeared to be The Mill, which also supplies the Red Door with its bread. So I assumed I had found the cradle of the toast phenomenon.

I was wrong. When I called Josey Baker, the — yes — baker behind The Mill's toast, he was a little mystified by the dustup over his product while also a bit taken aback at how popular it had become. "On a busy Saturday or Sunday we'll make 350 to 400 pieces of toast," he told me. "It's ridiculous, isn't it?"

But Baker assured me that he was not the Chuck Berry of fancy toast. He was its Elvis: He had merely caught the trend on its upswing. The place I was looking for, he and others told me, was a coffee shop in the city's Outer Sunset neighborhood — a little spot called Trouble.

The Trouble Coffee & Coconut Club is a tiny storefront next door to a Spanish-immersion preschool, about three blocks from the Pacific Ocean in one of the city's windiest, foggiest, farthest-flung areas. As places of business go, I would call Trouble impressively odd.

Instead of a standard café patio, Trouble's outdoor seating area is dominated by a substantial section of a tree trunk, stripped of its bark, lying on its side. The shop itself is about the size of a single-car garage, with an L-shaped bar made of driftwood. And a glass refrigerator case beneath the cash register prominently displays a bunch of coconuts and grapefruit. Next to the cash register is a single steel toaster.

Trouble's specialty is a thick slice of locally made white toast, generously covered with butter, cinnamon, and sugar: a variation on the cinnamon toast that everyone's mom, including mine, seemed to make when I was a kid in the 1980s.

Trouble's owner, and the apparent originator of San Francisco's toast craze, is a slight, blue-eyed, 34-year-old woman with freckles tattooed on her cheeks named Giulietta Carrelli. She has a good toast story: She grew up in Cleveland in a big immigrant family, her father a tailor from Italy, her mother an ex-nun. The family didn't eat much standard American food. But cinnamon toast, made in a pinch, was the exception. "We never had pie," Carrelli says. "Our American comfort food was cinnamon toast."

The other main players on Trouble's menu are coffee, young Thai coconuts, and shots of fresh-squeezed grapefruit juice called "Yoko." It's a strange lineup, but each item has specific meaning to Carrelli. Toast, she says, represents comfort. Coffee represents speed and communication. And coconuts represent survival — because it's possible, Carrelli says, to survive on coconuts provided you also have a source of vitamin C. Hence the Yoko. (Carrelli tested this theory by living mainly on coconuts and grapefruit juice for three years, "unless someone took me out to dinner.")

The menu also features a go-for-broke option called "Build Your Own Damn House," which consists of a coffee, a coconut, and a piece of cinnamon toast. Hanging in the door is a manifesto that covers a green chalkboard. "We are local people with useful skills in tangible situations," it says, among other things. "Drink a cup of Trouble. Eat a coconut. And learn to build your own damn house."

At first, Carrelliexplained Trouble as a kind of sociological experiment in engineering spontaneous communication between strangers. She even conducted field research, she says, before opening the shop. "I did a study in New York and San Francisco, standing on the street holding a sandwich, saying hello to people. No one would talk to me. But if I stayed at that same street corner and I was holding a coconut? People would engage," she said. "I wrote down exactly how many people talked to me." And cinnamon toast, she said, is a kind of all-purpose mollifier. "No one can be mad at toast," she said.

Carrelli's explanations made a delightfully weird, fleeting kind of sense as I heard them. But then she told me something that made Trouble snap into focus. More than a café, the shop is a carpentered-together, ingenious mechanism — a specialized tool — designed to keep Carrelli tethered to herself.

Ever since she was in high school, Carrelli says, she has had something called schizoaffective disorder, a condition that combines symptoms of schizophrenia and bipolarity. People who have it are susceptible to both psychotic episodes and bouts of either mania or depression.

One day in 1999, when Carrelli was living in San Francisco and going to school at the University of California, Berkeley, she took a long walk through the city and ended up on China Beach, a small cove west of the Golden Gate. A group of Russian men in Speedos were stepping out of the frigid ocean. And an elderly man was sitting on a towel, sunbathing in weather that suggested anything but. Carrelli struck up a conversation with the man, whose name was Glen. He told her that people swam there regularly, and that he sunbathed every day.

Carrelli left San Francisco shortly thereafter. But her encounter with the old man and the swimmers somehow made such a profound impression that five years later, she drove back across the country and headed for China Beach. When she arrived, she found Glen sitting in the same spot where she had left him. That day, as they parted ways, he said, "See you tomorrow." For the next three years, he said the same words to her pretty much every day.

Having spent muchof her adult life careening in and out of periods of homelessness and failing to maintain relationships with roommates and boyfriends, Carrelli found a kind of bedrock routine at China Beach. She started joining the swimmers every day, even in winter. And she began cultivating a network of people she could count on for help when she was in trouble — a word she uses frequently to refer to her psychotic episodes — while being careful not to overtax any individual's generosity.

Carrelli also found safety in simply being well-known — in attracting as many acquaintances as possible through coffee-shop jobs and random conversations. This gregariousness was in part a survival mechanism, as were her tattoos and her daily uniform of headscarves, torn jeans, and crop tops. The trick was to be identifiable: The more people who recognized her, the more she stood a chance of being able to recognize herself when she was in a dissociated state.

As Carrelli found her footing in the world, an idea began to take shape. At China Beach, she took to her notebooks, filling them with grandiose manifestos about living with guts and honor and commitment — about, she wrote, building her own damn house.

"Giulietta, you don't have enough money to eat tonight," Glen said, bringing her down to Earth. Then he asked her a question that has since appeared in her writing again and again: "What is your useful skill in a tangible situation?"

The answer was easy: She was good at making coffee and good with people. So Glen told her it was time she opened a checking account. He told her to go to City Hall and ask if they had information on starting a small business. And she did.

After having struggled as an employee in so many coffee shops, she now employs 14 people. In an almost unheard-of practice for the café business, she offers them profit-sharing and dental coverage. She hopes to one day open a halfway house for people who have psychotic episodes — a safe place where they can go when they are in trouble.

If the spread of toast is a social contagion, then Carrelli was its perfect vector. Most of us dedicate the bulk of our attention to a handful of relationships: with a significant other, children, parents, a few close friends. Social scientists call these "strong ties." But Carrelli can't rely on such a small set of intimates. Strong ties have a history of failing her, of buckling under the weight of her illness. So she has adapted by forming as many relationships — as many weak ties — as she possibly can. And webs of weak ties are what allow ideas to spread.

By John Gravois. ©2014 by Pacific Standard. Reprinted with permission.