It didn't take long for Laura Herrera to notice that something was strange about her twins.

At a routine 12-week ultrasound, the nurse stared long and hard at the lacuna between the silvery silhouettes on the screen before fetching the doctor. The archetypal identical twins lead separate lives even before birth, each with their own house and supply pipes. But Laura's fetuses shared a single amniotic sac and placenta unlike over 99% of twins, explained the doctor as she pointed a finger at the absence of a telltale line between the shadowy heads. They would have to keep Laura on close watch, and natural delivery was out of the question—the danger of umbilical cord entanglement and compression as the twins jostle and squirm often becomes fatal in the last few months.

On November 3rd, nearly 8 years ago exactly, Laura was whisked off for a planned caesarean at 33 weeks, the standard procedure for her monoamniotic-monochorionic (mono-mono for short) pregnancy. In the gloved hands of doctors, Eduardo and Fernando emerged from the womb perfectly mirrored, elbows and knees curled up snugly against their invisible line of symmetry to form a heart, blood-streaked cords snaking around them as a caduceus. Laura remembers hearing through the haze of partial anesthesia the beautiful simultaneity of their first wails—almost as if they’re entering the world as one.

In many ancient legends, twins represent the dualistic nature of the universe. The Mandika in Mali believe the Earth was created when an evil twin, Pemba, broke out of God's cosmic egg. In turn, the good twin, Faro, was sacrificed, and out from his fertile remains emerged life on Earth. Other twin stories emphasized their connection: Castor and Pollux from Greek mythology loved each other so deeply that Pollux gave up half his immortality to be with his brother when Castor fell to a spear. Together they grace our night sky, hand in hand, as the constellation Gemini.

The Yoruba people in Nigeria hold twins to especial regard, perhaps not surprising since they have the highest twinning rate in the world. In their traditional beliefs, twins share one soul, or ibeji, meaning "born of two." When a twin dies prematurely, a sacred wooden figurine is carved to represent the departed. If the figurine is not fed, clothed, and properly cared for, harm may befall the living twin, so strong the yoke that ties their fates forever.

Conjoined twins, of course, not only share the same genes and womb but also an unbreakable physical bond. Eduardo and Fernando were nearly fused themselves based on how long after fertilization the nascent embryo spontaneously split into two. Days 8-13: mono-mono twins. Days 13-15: conjoined twins.

But Laura would soon find out that even the most simple and ironclad rules of science and life can be defied. While still drifting between the interior of her hospital room and the twilight of exhausted slumber, she blinked and found herself on a wheelchair in the neonatal intensive care unit. Laura numbly clung to then-husband Mateo's hand as the nurses told her the twins rapidly faded after birth. Eduardo and Fernando were silently turning blue in their boxes, tiny bodies studded with far too many tubes and wires. As she watched in utter despair, she thought about how upsetting it must be to be pressed against your double in a gentle sea in one moment then ripped asunder into a lonely box the next. Can they go together in one incubator? She asked.

The staff must have been desperate, for they granted her seemingly irrational request. As soon as the nurses brought Eduardo and Fernando close to each other, they snapped their arms and legs together as if magnetized, drawing out weak matching cries through their thawing lungs. Laura found her own breath and laughed along through her tears. She knew then they would be all right.

Everyone shook their heads in amazement. "They have something magical between them," a nurse told Laura. "You should never separate them."

On a scorching summer afternoon last year, I knocked on a set of double front doors set in an otherwise ordinary Spanish-style house in Alhambra, California, all prickly stucco with a low red-tiled roof. Laura had emailed out of the blue, asking if we could write an article on her family, and I agreed to visit with no real idea of what to expect.

The doors swung open at the same time to reveal a petite woman with warm brown eyes, her crow's feet crinkling as she shook my hand. "Do you remember the list? Don't touch them unless at the same time," Laura rattled off the rules she sent earlier. "Try to look at the center of them. They don't like unbalanced things."

That must have been an understatement, I thought as Laura ushered me into the living room, a remarkable exercise in minimalist bilateral symmetry. Twin cabinets bracing the television greeted me from the entryway. The bathroom to the left sported paper rolls on both sides of the toilet and double toothbrushes and soap on the sink. The kitchen had a French door refrigerator and only one tabletop appliance: a blender with the labels taped over in which Laura makes soups and purees for most meals—unprocessed vegetables and meat are too inhomogeneous for the twins' liking. Laura poured us lemonade at the round dining table, four chairs arranged exactly equidistant from each other. Every surface was immaculate, the sole decoration on the wall a gold-framed icon depicting twin haloed saints.

"There's plenty of asymmetry in the world," Laura said, "so I want to make home as comfortable for them as possible."

Before we met the twins, Laura showed me her bedroom in the back corner, tiptoeing across the carpet almost conspiratorially. I understood why when the door opened: all of the disorder in the house is sequestered in a 10-by-10-foot explosion of color and fabrics and miscellany. Sketches and lopsided clothing in bright shades of teal and purple and orange plastered the walls. A large heap of containers and broken electronics grew from the foot of a tiny table—sewing machine perched delicately on top—in a dizzying, ceiling-grazing lattice. "When things aren't symmetric, they end up here," Laura smiled wryly.

After we settled back at the table, she told the twins to come out in Spanish—la periodista está aquí. The double saloon-style doors of their room swung outward, and Eduardo and Fernando walked across the kitchen as perfect mirror images, one pair of hands and feet joined at the axis of symmetry down the center linoleum tile. I felt a lightning bolt wind down my spine. It was as if someone had taken a pair of scissors to the folded fabric of spacetime, cut out one boy, then unfolded to make two.

"Hi," they said in unison, swinging their legs shyly. Eduardo waved with his right hand and Fernando with his left. Their other hands remained pressed palm-to-palm midway between them, like the paper chain dolls popular in elementary school. They looked exactly identical, mirrored from every strand of hair to the mole near Eduardo's left and Fernando's right eye down to the faded patches on their jeans.

"Hola. Cómo se llama?" I asked.

"Hugo," they said together, like two channels of a stereo speaker. Laura's email mentioned that they picked out the name at age six from their favorite series of adventure books featuring a boy and his dog.

"Encantada, Hugo." I tried my best with the silent H and the closed back rounded vowel U, crossing my arms to shake their outer hands simultaneously. The twins beamed.

I shook out a deck of cards from my purse and told them we would be playing a game where they couldn't see each other. As they maneuvered themselves to the floor, wriggling back-to-back, I dangled two random cards in front of them: Queen of Spades for Eduardo and Three of Hearts for Fernando.

"What card do you see?" I asked.

They tittered and said a jumble of words in unison. "The queen of-three of-heartspades!"

"Do you like seeing different things from each other?" I asked.

They shook their heads together. "No! It's weird!"

Next, I handed them two line drawings of Captain America and a double pack of markers. They reached for forest greens simultaneously and began attacking the papers with much more enthusiasm than respect for boundaries, like your typical eight-year-olds. When they finished, I flipped one drawing over and overlapped it over the other, holding the papers up against the window to confirm that the coloring pattern was indeed identical and mirrored. There was no way they could have coordinated each zigzag to be the same in shape and pressure, not to mention hundreds of them, with their backs to each other.

Having passed my tests with flying colors, the twins ran off to play a video game while I tried to make sense of what I'd seen. From the rumors I heard about them, I thought perhaps a distorting game of telephone had fabricated a myth out of two boys with merely an extremely strong connection, like anecdotes of twins who finish each other's sentences, get the same unlikely injuries, or share thoughts and emotions. But this was clearly something more.

As the twins mashed the buttons on their mirrored controllers, their jaguar avatars moving as one through an obstacle course, Laura told me that they described themselves as one person as soon as they could talk. She wasn't surprised: from day one, they could not be separated and balked at non-simultaneous food or diaper changes. The pediatrician brushed off Laura's concerns as exaggerations of an over-imaginative new mother, but devoutly Catholic Mateo was terrified the twins were cursed somehow. Laura came home from work one day to find him hovering over the twins' bed with a strange man who was purporting to exorcise the evil spirit in them. Furious, she threw both out of the house and warned them to never return. In the very same week—semana del infierno, as Laura calls it—she was fired from her pattern maker job at a clothing label for too many twins-related absences. Her mother María, who thought Eduardo and Fernando were blessed by the twin Saints Cosmas and Damian, moved in to watch the twins while Laura desperately found three temporary jobs, working endless shifts seven days a week just to keep the family afloat.

“It wasn’t easy,” said Laura with no little understatement, and for a while we watched flotsam of her old pain wash ashore.

Tucked under apple trees in a suburb of Hartford, Connecticut is an unassuming white building. A small and steady stream of families flows through the doors every day, each hoping for a miracle. The waiting room upholstery is a sleek slate gray, perhaps not the bright primary colors you might expect at a children's clinic, but the visitors hardly notice: their eyes train for a man at the end of the hall.

Bruce Freedman is something of an enigmatic rock star among child psychologists. His website lists his awards and successes in splashy profiles: seven-year-old non-verbal A. who began speaking for the first time, ten-year-old C. cured of her compulsion to eat paper, plastic, and even glass. But it's far scantier on methodology, with vague descriptions such as a combination of cutting-edge science and psychotherapy.

"He's solved difficult cases that have confounded many others, but he holds his cards close to his chest," said Diane Garabedian, a neuropsychologist at Harvard Medical School. "With that comes accusations of abuse. His lack of transparency might just be him being protective of his methodology, or maybe he can't tell us because we'd all be outraged."

Most families of Freedman patients seem to tell a different story. Those whose children saw improvement worship him with something close of a cult-like reverence; even the ones whose children didn't generally cited incompatibility rather than any wrongdoing on his part. No one I contacted would reveal what happened at his sessions, citing both privacy concerns and not wanting to break Freedman's trust.

"Therapy is never pretty, especially with children with difficulties," said Freedman, sharp eyes peering through thick glasses from his mahogany desk when I asked about his methods, allegedly including yelling at, slapping, and restraining children. He declined to comment on any specific methods and maintained that everything he does is with the full knowledge and consent of the parents.

As the twins began to walk and run, María found them increasingly harder to watch. One day, Fernando hit his head hard on the kitchen counter as they ran through the living room, causing the twins to bawl for a day straight until the swelling went down. Family and friends urged Laura to seek medical opinions, and Laura took them to one puzzled pediatrician after another—the twins were healthy and meeting their developmental milestones, but doctors could no longer dismiss their synchronicity as mere fantasy. Finally, one referred her to Freedman, touting him as a miracle worker for the most impossible cases

Laura thought that if there was any chance he could find out what was wrong, she owed it to the twins to try. She frantically gathered money from relatives for the trip and begged her employers for a few days off. Despite the terrible flight—TSA agents tried to pry the twins apart for the security screening and the airline lost their luggage—she was buoyed by her first encounter with Freedman. "He told me I had done the best I could for my children," said Laura, "and now he would try the best he could to help them."

The twins were three then. "It was like seeing doppelgängers when they first walked in. Completely eerie," he recalled. Freedman had his own list of hypotheses prior to meeting them, from psychosomatic syndromes to mirror-touch synesthesia, a rare condition in which an individual experiences the same sensations that they observe another person experiencing. Seeing someone else stub their toe would cause you to feel a phantom pain in yours, which would explain the reaction of the twins to the injury.

After significant cajoling, the twins went in an MRI machine squeezed against each other. The scans revealed that they were perfectly mirrored in their internal organs as well, a rare but not unheard phenomenon among identical twins, particularly mono-mono ones.

Mirror image twins are not officially defined because there is a wide range of mirrored-ness, according to Katherine Luo, an expert in twin studies at the University of California, Berkeley. "Some may be mirrored in handedness, for example, but they will be completely different in other attributes," she wrote. "It's difficult to systematically study." The MRI scan did not reveal any other medical conditions or explanations for their synchronicity. Laura refused more invasive testing, but consented to a genetic panel that would search for rare abnormalities and conditions.

Freedman's next test was simply to film the twins as they played to see if one twin was merely copying the other. If that were true, one set of movements must be slightly delayed in time from the other twin's by the human reaction rate, approximately 0.2 seconds. In international track and field competitions, runners who leave the blocks less than 0.1 seconds after the gun is fired are disqualified, because it's deemed impossible for them to be purely reacting to the gun.

He showed me the frame-by-frame archival footage of the twins playing and talking, recorded using a slow-motion camera. At the rate of five hundred frames per second, a hundred times quicker than human reaction time, the twins talked and stacked Legos exactly the same way at exactly the same time. This ruled out simple mimicry or synesthesia, but Freedman still believed it was possible that they timed their actions to background cues. He wanted to see what they would do in separate rooms.

Laura had not been told the exact nature of the next experiment, only that they needed to test the twins' behavior without her presence. She looked on anxiously as a resident ushered them into a dark hallway and closed the door behind him. There the hidden camera provided the other view: in a testing room, two researchers tried to ply the twins with a toy giraffe without success. They proceeded to separate the twins, dragging Fernando out of the room and into another as both kicked and screamed. As soon as they lost sight of each other, the twins broke down into the biggest tantrums I have ever seen, flailing violently on the ground. It was uncomfortable to watch, but something stranger was about to happen.

With a few clicks of the mouse, Freedman converted the audio waveforms recorded by the identical microphones in both rooms into a series of red and blue spikes. At first, they were completely identical and overlapping. When one researcher tried to press a stuffed bear into Eduardo's hands, both shook violently and cried even harder. But around minute two, the first aberration can be seen: after taking a synchronized breath, Fernando cried a split-second after Eduardo. Gradually, they became more and more out of sync. At the end of the five minutes, their cries were noticeably different in pitch and amplitude, not just phase.

Outside, Laura asked to stop the experiment as soon as she heard the cries. The resident accompanying her waved the consent form she signed, telling her she had authorized this and that it wouldn't take much longer.

"How long?" Laura pressed. A few minutes more, he said.

"A few minutes feels like forever when your babies are suffering, you know? I couldn't believe that this guy had no feelings. He was just letting three-year-olds cry their hearts out in the name of 'science', even after I told him they could not be separated," Laura recalled, her voice shaking.

Finally, Laura protested loud enough that the resident called Freedman, who was observing the video and audio feeds from a separate room, and asked what to do about the "upset lady." Freedman told him to stall.

"The twins were just starting to become noticeably out of sync," Freedman remembered. "I wanted to see if one would stop his tantrum sooner."

Laura was beyond waiting and pushed past the resident. "It was the worst thing I ever had to do," she teared up in remembrance. "I literally had to drag them out of the rooms by their legs because they could not be picked up."

On the video feed I watched Laura, in hysterics, pulling blurry windmills of limbs and tears out of each room. The hallway was not videotaped, but the audio continued. As soon as the twins were outside, their crying began to sync up. As they slowly calmed over the next ten minutes, the only sounds were sniffling and Laura sobbing lo siento, mijos over and over.

Laura immediately terminated the study and took her children home. Four weeks later, she received a letter in the mail. The twins had no genetic abnormalities of any sort. That was the last communication she received from Freedman.

Hugo doesn't remember the incident, but they do know the feeling of briefly separating for a split second from tripping over uneven ground. "It hurts really, really bad everywhere," they said, gesturing from head to toe.

I asked Freedman if he regretted his methods. He went quiet for a while, staring out the window at the rustling leaves.

"I regret that Mrs. Herrera feels I did something wrong and unethical," he finally spoke in a heavy tone. "My intentions are far from that. I understand the experiment was distressing for her, but crying for five minutes has never harmed a child. I wish I could repeat the experiment with the twins sedated before their separation."

He pushed up his glasses and folded his arms. "I know that Laura thinks I'm a monster, and you are clearly telling the story from her point of view. But it's not as simple as that. It's cruel she supports their delusion when they are clearly two separate individuals."

Laura shook her head when I relayed Freedman's comments. "He knows nothing. They nearly died at birth, remember? Hugo will start crying if you separate them, no matter how sedated. There's only one explanation. They really are one person born into two bodies."

"Where does the light of the Moon come from?"

The twins raised their opposite hands, two mirrored desks pushed together so they can remain in contact, arm and foot. "The Sun!"

"Very good, Hugo," their homeroom teacher smiled. When he told the class to turn to page 43, Hugo's neighbors helped them flip their book.

"I tried to read Fernando's homework with a mirror at first. Then I realized it was always going to be identical to Eduardo's, so I just grade Eduardo's—I mean Hugo's—now," he told me. The twins write Hugo in opposite upper corners of the paper and are allowed to remain together during exams. "The kids are very accepting, actually—the class convinced me to call them Hugo because that's their chosen name."

Every fall, Sunny Hills Elementary School holds a meeting with Laura, Hugo, and their new teachers, where Laura carefully explains the accommodations that must be met. "The school has been amazing," she gushed. Hugo has special permission to skip intense contact sports—Laura does not want one of them to get an injury—but they enjoy running while touching palms. They read books together on a special tablet with symmetric buttons while their classmates throw dodgeballs during P.E. class. "And sometimes they play fútbol too and think I don't know," Laura grinned at their abashed face.

"Hugo told us they were one person," said Veronica, a classmate. "I thought that was kind of weird at first. But they definitely do everything together like one person. It's really cool."

"Sometimes other kids are mean to me," Hugo told me. "They think I'm cheating on tests because I'm two people. But I prove I'm one person to them by doing stuff at the same time that no one else can do. Then they shut up and believe me."

A year ago, Laura began receiving emails from an odd cross-section of society: doctors, media, and curious laypeople. She was aghast to find that Freedman's latest book, Psychotherapy for a Better Life, contained a section about Hugo and her. It presented his version of their visit, ending with a lament that Laura did not consent to further research. Though their names were changed for privacy, some Internet sleuths put together the details from the book and found Laura's contact information.

She woke up her creaky six-year-old laptop to show me her email folder labeled 'crazies', still averaging a few messages each month. People claiming to be doctors writing from the world over offering diagnoses and treatment. Requests for appearances on television, which she steadfastly ignores—"Hugo's not a circus animal." People who confidently present their theories from reading Wikipedia.

Perhaps the strangest is a two-hundred-page thesis from a man claiming her twins are the manifestation of quantum entanglement at a macroscopic scale, which proves his theory that we are all connected by the quantum consciousness (several physics professors confirmed to me that entanglement cannot happen on a human scale, though they could not explain Hugo's condition either).

You know this piece will only make the attention worse, I told her, and she nodded. "I can't just let Freedman tell lies about me and my son," she shook her head. "I want to tell my side of the story."

I asked if she might ever consider a more ethical medical test in the future with full consent from her and Hugo. "People always tell me I should try again," she sniffed with no small disdain. "But there's nothing wrong with my son. They are exactly how they are. I made that mistake once. That was enough."

Hugo materialized at the table with two bottles of juice, which Laura unscrewed and returned with both hands before I could blink. I thought about all the daily activities we take for granted that cannot be done mirrored, which Laura is well aware of. She rattled off her parenting to-do list, a mix of the mundane and extraordinary. Cut back on American television and video games. More Spanish practice. Teach them to cut their own hair and open normal doors—she thinks with enough practice, one can turn the handle while the other mimes the action.

The bigger problems linger in the back of her mind. Hugo will have two identities in the eyes of the state despite how they personally feel. Any job where they cannot stay in constant contact is out of the question.

"I'm not always going to be here," she clicked her nails on the counters pensively. "They'll have to take care of themselves, and I have to prepare them best I can."

She was undoubtedly thinking about María, who passed away last year after a short battle with late-stage breast cancer in a terrible blow to the family. In the aftermath, Laura found a part-time position as a bank teller so she can be with Hugo when they are back from school. At night, she answers customer support calls for various companies on her headphones while stitching skirts and tops on her tiny sewing machine.

"Thank God for the Internet," Laura laughed as she showed me the impressive sales numbers of her online store. Business was picking up, the bold and somewhat ironic asymmetry of her clothing—colorful one shoulder tops and diagonal ruffle skirts—becoming her trademark. She hopes to one day quit her day job and sell her designs full-time, her dream since she was Hugo's age.

While Laura answered customer inquiries in her room, I watched Hugo play their video game, wondering what it's like through their eyes. Does Fernando's eyes see the world flipped from Eduardo's? Does that question even make sense if they are indeed one person, like the Yoruba ibeji? Perhaps, as an uncleavable whole, they experience things just like the rest of us: that is, within the wide range of possible human experiences but still idiosyncratic in their own way.

I want to be an astronaut, the twins said, just like Book Hugo, who solved a murder mystery in space in the latest installment. Above their bed was a large sketch spanning two sheets of paper depicting two astronauts in special spacesuits connected at the hand floating in a sea of scribbled stars, identical spanners in the opposite hands. "I won't ever be hit by space trash because I can see 360 degrees," Hugo grinned as their jaguars jumped off the platform, went through the final hoop, and reached the flag together.