On Aug. 19, 1946, Dorothy Dennison left her house to walk to the local butcher’s shop. It was a Monday afternoon, and the high school student was on summer break. She arrived at the butcher’s shop around noon and purchased some hamburger steak, which her mom planned to fix for dinner that evening.

Hours passed, and Dorothy did not return home. Alarmed, her mother telephoned a neighbor and the butcher, but neither had any leads on where Dorothy could be. At 5:25 p.m., the mother phoned the police to report her daughter missing.

Days passed, but no clues emerged. Finally, on Friday, Officer Patrick Sullivan found her in the darkened home of a church rector who was on vacation. Behind shuttered windows and amid covered furniture, Dorothy lay on her back, dead.

Her arms and legs were spread, and a knife stuck out of her gut. Her white dress had been pulled open, exposing her chest, and bite marks covered her body and legs. Blood had seeped from wounds on her head, haloing her brown hair in a dark pool. She was still wearing the red hair bow and matching ballet slippers that she had left the house in on Monday.

At Maryland’s Office of the Chief Medical Examiner, I look down at Dorothy’s crumpled body, exactly as it was when Officer Sullivan found her at 4:15 p.m. on Aug. 23, 1946. Dorothy’s tragic end has been preserved forever in a bizarre miniature diorama that captures each physical detail surrounding her death.

Dorothy’s deathscape—dubbed the Parsonage Parlor—is one of 20 dollhouse crime scenes built by a woman named Frances Glessner Lee, nicknamed “the mother of forensic investigation.” Lee’s murder miniatures and pioneering work in criminal sciences forever changed the course of death investigations.

Lee, who went by the name Fanny, was born in 1878 to millionaire parents who made their money selling agricultural equipment. She grew up in Chicago and later said she suffered from a sheltered, lonely childhood. When Lee was 4 years old, her mother—also named Frances—recorded in her diary that her daughter had stated, “I have no company but my doll baby and God.” Along with her older brother, she was home-schooled in a fortresslike house that one architect described as “pathologically private.” Lee learned feminine skills such as sewing, embroidery, painting, and the art of miniatures from her mother and aunts, but at the same time had a fondness for Sherlock Holmes stories and medical texts.

Lee’s parents were firm believers that a woman’s place was in the home, so after her brother left for Harvard University, Lee’s requests to also attend school were rebuffed. As her father liked to say, “A lady doesn’t go to school.”

Thus began several decades of mounting bitterness and regret. Although she continued to harbor dreams of becoming a doctor or nurse—of “doing something in my lifetime that should be of significant value to the community,” as she later wrote—shortly before her 21st birthday, she married Blewett Lee, a lawyer and professor at Northwestern University. The couple had three children, but things soon fell apart and they divorced in 1914, which was a scandalous turn of events at the time.

Despite being free of an unhappy marriage, years passed before Lee could truly come into her own. She was dependent on her family for financial support, but in 1929, that began to change. Her brother passed away, and a few years later her mother followed him to the grave. In 1936, her father died, passing on the family fortune to his daughter.

As her daughter-in-law later attested, Lee, meanwhile, had begun nursing a passion for forensics, inspired by one of her brother’s friends, George Burgess Magrath, who served as Boston’s medical examiner and was famously skilled at solving perplexing murder cases of the day. When Lee realized she was free to direct her energy and resources in whatever direction she chose, her thoughts immediately turned to the stories he had told, and to his complaints that murders too often went unsolved because detectives misinterpreted or tampered with evidence or coroners with no medical training botched autopsies. “Investigators used to do dumb things,” says Bruce Goldfarb, a spokesman for the Maryland medical examiner’s office. “They would walk through blood, move bodies, and put their fingers through bullet holes in clothing.”

Lee decided to take it upon herself to reform the country’s legal medicine system. As a start, she donated money to Harvard to create a professorship for a legal medicine expert—which Magrath filled—and also created the George Burgess Magrath Library of Legal Medicine, which was soon followed by the country’s first forensic pathology program. Although Magrath passed away two years later, through her own research and outreach, Lee became regarded as an expert in the field. She never forgot her source of inspiration, however. As she wrote in a letter in 1951: “I found that no one … knew exactly what legal medicine was supposed to mean. … But fortunately with the skill, knowledge and training of Dr. Magrath to guide me (he, in turn, really started from scratch), I have been able to accomplish a good deal.”

Despite these successes, however, Lee felt that more was needed to teach students the emerging art of evidence gathering. It was impossible to bring them to crime scenes, so Lee decided to create her own miniature crime scenes to use for training. She called her creations the Nutshell Studies of Unexplained Death. “She came up with this idea, and then co-opted the feminine tradition of miniature-making to advance in this male-dominated field,” says Corinne May Botz, an artist and author of The Nutshell Studies of Unexplained Death. “Like Sherlock Holmes, she was setting a scene and creating something like a character study of the victims, and she went about doing this very much from a detached investigator’s point of view.”

The 20 models Lee created were based on actual crime scenes, and she chose only the most puzzling cases in order to test aspiring detectives’ powers of observation and logic. Moreover, many of the cases could not be solved by observing the crime scene alone, demonstrating the need to involve medical examiners and other scientific experts in the process of solving crimes. While some—like poor Dorothy Dennison—were most definitely the victims of foul play, others could have died of natural causes or suicide. It was up to the detectives to find out.

Lee spent $3,000 to $4,500 creating each model, and her obsessive attention to detail shows. Grime from countless unseen hands coats light switches and door handles in cheap motel rooms while contemporary 1940s and ’50s food products line kitchen shelves in more affluent homes. Calendars are turned to the correct month and year that victims died; tiny keys fit into doors that can actually be locked and unlocked; and even a fingernail-sized mousetrap works. A miniature rocking chair rocks exactly three times when it was pulled back to a 45-degree angle, to meet with specifications from the real-life crime scene. “She was nuts about the level of detail,” Goldfarb says.

As for the homicides themselves, Lee attended autopsies, visited crime scenes, and studied blood spatter patterns. She made sure that her corpses possessed the correct degree of bloat and discoloration and that the evidence she was portraying—whether the angle of a knife or the pooling of blood—matched the mysterious circumstances of the deaths. She depicted an eclectic array of mortal endings, from hangings to falls to fires to gas-oven suicides. She often portrayed victims who were far removed from her own experience in life, such as drunks, prostitutes, and the poor.

On the other hand, Botz points out that most of the victims are female, and many died in their homes. Gender and the home, of course, were major themes in Lee’s life. Some scenes hint at their creator’s personal life and interests, too. Like the room depicted in the Nutshell “Pink Bathroom,” Lee also had a pink bathroom in her home. She also enjoyed fish imagery—the wallpaper motif in that scene. “There was an interplay between factual documentation and imaginative fiction,” Botz says. “Her own biases came into play.”

For the larger items—the houses themselves, the roofs—Lee enlisted the help of her carpenter, who followed her specifications exactly. The roof of the “Barn” Nutshell, for example, came from pieces taken from a 200-year-old barn on Lee’s own property, ensuring that it was authentically weathered. With her carpenter’s help, she turned out up to three crime scenes per year.

“She’d have been less frustrated if she had been born today, but it’s lucky for us, because the models are a result of her own personal time and culture, of her Victorian sensibilities and its emphasis on domestic space and family life,” Botz says. “All of these things came together to shape the models.”

In 1945, Harvard installed the first of Lee’s models, and she began delivering biannual, weeklong seminars that used them as training tools. Lee was almost always the only woman in the room. After some initial reluctance, she came to be accepted. She wined and dined her new colleagues, and many of the detectives grew fond of her, sometimes referring to her as “Mother” and sending her Mother’s Day cards. She even became an honorary captain with the New Hampshire State Police, making her the first woman to join the International Association of Chiefs of Police. Most significantly, though, her work mattered. Careful evidence gathering became a quintessential part of investigations, and several states amended their legislation to require better-trained coroners and medical examiners. As Goldfarb says, “She made forensic investigation into a scientific process.”

Lee died in 1962 at the age of 83, and the endowment for the Harvard program ceased. The university shuttered its forensics program and put the Nutshells into storage. They were likely headed for the dumpster, when Harvard professor Russell Fisher accepted a job in Baltimore as Maryland’s chief medical examiner. He brought the Nutshells with him, and in 1968, began using them in teaching seminars. Today, they are permanently installed on the fourth floor of the Office of the Chief Medical Examiner, behind a door marked “Pathology Exhibit.” The Nutshells are still used as training tools in homicide seminars. “This is not a museum or a gallery, it’s still functional,” Goldfarb says of the exhibit. “Death doesn’t change.”

Lee has a dedicated and growing following. She was the inspiration behind the character Jessica Fletcher in Murder, She Wrote, and a CSI episode was inspired by her work. Recently, Guillermo del Toro contacted Botz about optioning the rights to create an HBO show about Lee.

Although the Nutshells are not available for public walk-ins, they do get plenty of visitors, ranging from detectives to artists to miniatures aficionados. Paging through a guest book kept on top of the “Three-Room Dwelling” Nutshell—a possible double-murder and suicide that includes an executed infant—a column asking for purpose of visit contains a range of answers, from “artistic curiosity” to “DMort3 Training” to “love.”

Now I, too, have stumbled upon Lee’s intriguing story and perplexing creations, thanks to a field trip organized by the New York–based Morbid Anatomy Library and Museum. Back at the Parsonage Parlor, I am still mulling over what happened to Dorothy. I try to put myself in the detective’s place, to imagine walking into the diorama as a 5-inch-tall figure, as Lee used to instruct of her trainees, and to use my senses to infer information about both Dorothy and her killer. Temperatures, Lee points out in the text contained below the Nutshell, exceeded 90 degrees that week. Dorothy’s body, accordingly, is beginning to show signs of decomposition, mirroring the now-rancid hamburger steak that neatly lies on a nearby chair along with her purse. The blood pooling around her head indicates that she died in that room, but there are no signs of struggle in the room. A hammer smeared with a trace of blood lies near Dorothy’s corpse, but then there’s the knife—which was the actual murder instrument?

So was it the butcher who did it, or perhaps the parson, who was supposedly on vacation at the time? Or maybe a secret lover? Most likely, someone she knew lured her in, willingly, to her death, since the purse and meat placed on the chair indicate a casual, relaxed encounter. The bite marks and position of her body suggest a sexual assault, but only a postmortem analysis will reveal whether Dorothy was raped. The teeth marks might help identify her killer by comparing imprints with suspects’ dental records, and if Dorothy had been murdered today, genetic testing could lend clues about her killer’s identity. High-tech tests are not needed to solve this crime, however: According to a 1966 story published in the Harvard Crimson, there is a solution.

But as frustrating as that lingering mystery might be, the answers to the Nutshells are kept secret to preserve their usefulness as training tools. Unless we solve the crime ourselves, we are left to wonder, as I am still doing myself. “Wanting answers is natural,” Goldfarb says. “Everyone wants to know the answers.”

Simply answering the riddle, however, is not the point. As Lee once wrote herself, “The Nutshells Studies are not presented as crimes to be solved. Rather, they are designed as exercises in observing and evaluating indirect evidence, especially that which may have medical importance.”

Sometimes those observations can lead to a well-savored answer, but other times, more information—whether through an autopsy or interrogations—is needed. In other cases, the mystery cannot be solved with certainty, reflecting the grim reality of crime investigations. But whatever the circumstances, the investigator, Lee wrote, is tasked with “seeking only the facts—the Truth in a Nutshell.”