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The 911 call came in at 5:55 p.m. on September 29, 2012. A woman had fallen from a ledge in Rocky Mountain National Park; she was alive but unconscious. “I need an alpine mountain rescue team immediately,” said the woman’s husband, a slight quaver in his voice.

A middle-aged couple from the Denver area, Harold and Toni Henthorn had been celebrating their anniversary with a weekend trip to Estes Park when their afternoon hike turned tragic. As Harold’s cellphone battery dwindled, the dispatcher coached him through CPR protocol. Harold was calling from a remote location on the park’s Deer Mountain, about 2.5 miles from the trailhead and at the base of a roughly 150-foot cliff.

While he waited for first responders to reach him in the backcountry, Harold built a small fire and began texting family friends, according to , a 2017 book about the incident: Urgent…Toni is injured…in estes park…Fall from rock. Critical…requested flight for life. Emt rangers on way. At 6:25 p.m., he sent an update: Pulse 60, Resp 5. One hour later: Can’t find pulse.

It was close to 8 p.m. and dark by the time park ranger and EMT Mark Faherty neared the couple’s location, according to court documents. He picked his way over boulders and downed pines until he finally saw Harold feebly attempting chest compressions on his wife. When Faherty examined Toni, her pupils were fixed and dilated, and she had no pulse. Faherty convinced Harold to hike out with him that night, promising that the other rangers who had by this point arrived at the scene would stay with Toni’s body until daylight, when it could be safely removed. It took the two men—the grieving husband and the ranger—a little over two hours to make their way back to the trailhead.

At first, the accident seemed tragic in a routine way; many people fall to their deaths in national parks every year. But over the next few days, as Faherty dug deeper into the case, several things struck him as strange. For instance, the timeline Harold gave didn’t line up with the evidence. And other details seemed off, too, like how Harold insisted he’d given his wife CPR, but Faherty recalled that her lipstick had been unsmudged when he arrived on scene. Faherty asked Harold about his previous marriage. His first wife had died in an accident, Harold said. He was reluctant to talk about it.

Around the same time, Rocky Mountain National Park and other law enforcement agencies started getting letters and phone calls about Toni’s death. Some were anonymous, others came from people who identified themselves, but all made pretty much the same point: there was something suspicious about Toni’s death. Harold’s first wife had also died in an incident in a remote area, to which he’d been the only witness, some writers pointed out. “Sadly, there are many similarities to these two accidents,” one unsigned note read, according to the 2017 book . Thanks to generous insurance policies, Harold had been awarded more than half a million dollars after his first wife’s death. Toni was even more heavily insured. In Harold’s car, which had been impounded right after the accident, an investigator found a park map with the Deer Mountain trail highlighted and an X marking the spot where Toni fell.

The case had just gotten a lot more complicated. This was a suspicious death in the backcountry. Any day now, the area would get its first major snowfall, rendering the possible crime scene inaccessible for months. So Faherty called in the (ISB).

The elite special agents assigned to the ISB—the National Park Service’s homegrown equivalent to the FBI—are charged with investigating the most complex crimes committed on the more than 85 million acres of national parks, monuments, historical sites, and preserves administered by the National Park Service, from Alaska’s Noatak National Preserve to Hawai’i Volcanoes National Park. They have solved homicides, tracked serial rapists hiding in the backcountry, averted kidnappings, and interdicted thousands of pounds of drugs. They’ve busted a reality TV host who and infiltrated theft rings trafficking in looted Native American artifacts. But the ISB remains relatively unknown to the general public and even to fellow law enforcement. Local cops and FBI agents are sometimes baffled when Yosemite-based ISB Special Agent Kristy McGee presents her badge in the course of an investigation. “They’ll say something like, ‘What do you guys investigate? Littering?’” she told me recently. ��

There’s a pervasive idea that crime doesn’t happen in our national parks, that these bucolic monuments to nature inspire visitors to be more noble, law-abiding versions of themselves. But parks are filled with people, and people commit crimes. Millions of visitors pass through national parks every year (Yosemite alone saw over 4 million visits last year), and despite the trill of birds and the majesty of the redwoods, they misbehave in ways that would be familiar to any big-city detective: they drive drunk, they rape, and they assault. “People who abuse their kids at home come to the park and they abuse their kids here,” McGee says.

The baroque, headache-inducing way jurisdiction functions in the United States means that, generally speaking, when crimes are committed on Park Service land, the county sheriff or local cops may not be in charge; the park service would be. There are more than a thousand park rangers with law enforcement training who handle most of the day-to-day trouble, but when a case gets serious, the ISB steps in. Sometimes their work is akin to that of the FBI: investigating crimes committed by some of the millions of park visitors. In other cases, the work is more like that of a small-town sheriff’s department: tips whispered at the grocery store, agents arresting people whose kids attend the same day care as theirs. “Yosemite is a small town,” ISB agent Steve Kim, who’s based in the California park, told me. “Which means it’s a minefield. And it helps knowing where the mines are.”

ISB agents face other challenges non-park cops don’t. While an FBI investigation can draw from a force of about 35,000 special agents, intelligence analysts, IT experts, and forensic technicians, there are precisely 33 ISB agents covering the entire United States. While frontcountry criminals usually have the courtesy to break the law indoors, the ISB’s crime scenes may be at the bottom of a steep cliff or in the middle of a rushing river. The perennial underfunding of the Park Service means that while FBI agents dress in sharp suits and travel to crime scenes in huge vans stuffed with high-tech equipment, ISB agents often have to lug their not-quite-state-of-the-art gadgetry through the woods on their backs—sometimes at night, in the rain.

But while the scrappy nature of the ISB is one of its major challenges, it is also, its agents insist, an advantage. “We have the best job, because we get to put all the pieces together,” McGee says. “If you’re working for the FBI, you might have a piece of the puzzle, but someone else might go do the interview, and someone else might do some other part [of the case]. That’s more efficient—you can get things done faster that way—but we just don’t have those resources. You go over the initial report. You’re involved with the evidence. You’re involved with each step of the investigation.”

As suspicion mounted around Harold Henthorn, the ISB’s regional office in Colorado took charge of the investigation. There are so few ISB agents covering so much ground that most of them work solo. In this case, the ISB “office of one” assigned to Rocky Mountain National Park was Beth Shott, a 20-year Park Service veteran with a graying ponytail, freckled arms, and a reassuring air of competence. Shott grew up in Long Island, went to art school, and got a job in advertising. When she became extremely stressed while working on a Teddy Grahams commercial, she decided it was time to make some drastic changes to her life. Shott bought a truck, moved out west, and eventually began picking up seasonal Park Service work. “Every six months it was a new park, a new adventure,” she said. Shott quickly realized that the best way to guarantee that she got to work in the backcountry was to take a law enforcement job, which meant getting certified at the federal law enforcement training facility in Georgia. “I asked myself, can I wear a bulletproof vest? Can I shoot someone if I need to? And the answer was yes.”

During her career as a law enforcement ranger, Shott discovered that she had a particular aptitude for investigations and applied for a job with the ISB. That’s how, more than 20 years after that Teddy Grahams commercial, she found herself retracing a dead woman’s steps along the Deer Mountain trail.

Harold had told Faherty that he and Toni had planned to hike to Bear Lake, a popular half-mile loop with a gentle grade. It was the couple’s 12th anniversary, and they were staying at the posh —the place that inspired Stephen King to write The Shining. But Bear Lake had been too crowded, Harold claimed, so they made a last-minute decision to hike Deer Mountain instead. This struck Shott as odd. Deer Mountain was a very different trail, a 6-mile out-and-back hike with more than 1,000 feet of elevation gain. As Shott would learn later, Toni had bad knees and wasn’t particularly outdoorsy; friends described her as more of a walker than a hiker.

The couple then made another strange, spontaneous decision. According to Harold, when the trail plateaued after a mile and a half, he and Toni veered into the woods in search of privacy for, “romantic time,” as prosecutors would later call it. A few days after Harold told this to Faherty, Shott thrashed her way through the underbrush, following their path as best she could. Clearly, this was not some unmarked but common alternative route; it was studded with stumpy pine trees, and the terrain made for hard going. Shott tried to imagine herself in Toni’s place: a woman in her fifties, married for more than a decade, suddenly so overcome by lust that she absolutely needed “romantic time” on this extremely uncomfortable ground. Shott hadn’t gone far before the trees closed in behind her and she could no longer see the trail.

Next, Shott scrambled up a slope to the rocky shelf where Harold claimed he and Toni had stopped for lunch. The trailless exploration was difficult and Shott moved gingerly over lichen-spotted boulders. Harold had said that, after lunch, Toni spied a flock of wild turkeys she wanted to photograph. Toni had allegedly picked her way down a channel full of loose rocks, so Shott did, too.

At the bottom of the slope, Shott found a small, flat stone outcropping with enough room for one person to stand comfortably. Like a crow’s nest, she later thought. In front of her, the sheer cliff face dropped about 150 feet, but the platform felt safe enough, with a short rocky ledge serving as a kind of barrier from the sheer drop. Harold’s story was that Toni had been posing for a picture, then toppled backward to her death. Peering over the edge where Toni fell, Shott felt dizzy. She’d later find the dead woman’s blood still visible on the ground below. According to the coroner, Toni had sustained a number of injuries serious enough to kill. “She fell so hard she punctured her breast implant,” Shott told me later. “She lacerated her liver. She was basically scalped. She had a cervical fracture that could have affected her breathing. Her head wound was massive. Do you know what exsanguinated means? She bled out. The coroner, when he did the autopsy, had a hard time getting a blood sample off her because she had no blood in her system.” The coroner estimated that Toni had died between 20 minutes and one hour after impact.

When Shott first heard Harold’s version of how his wife died, she was skeptical but thought that, despite the incongruities of his story, there was a slight chance things had happened the way he claimed. But after she followed in the couple’s footsteps, she made up her mind. The terrain was so unforgiving, the couple’s decisions so inexplicable, the story so improbable, that she was convinced: Toni didn’t fall. She was pushed. Shott just had to figure out how to prove it.

The ISB’s roots can be traced back to on Memorial Day weekend 1970 at Stoneman Meadow in Yosemite National Park. At the time, rangers were thought of as generalists, equally comfortable with enforcing rules, building trails, and leading nature walks. But when the hippies congregated in the meadow—getting naked, playing tag, doing drugs, camping without permits—the rangers realized they were in over their heads. On July 4, park officials put up signs announcing the closure of the meadow at 7 p.m. “due to extreme litter and noise.” But the crowds didn’t disperse.

It was two months to the day after the , and tensions in the park—and the nation—were running high. At the designated time, the rangers, who had little experience or training in dealing with crowds, charged in on horseback. They tackled protesters and beat them with batons; the crowd flung glass bottles back at them. A cloud of tear gas settled over the meadow. Eventually, the rangers retreated and called for backup from neighboring police departments. It was a high-profile debacle, and it left Park Service higher-ups convinced that the agency needed a more professional law enforcement presence.

Over subsequent decades, the NPS enlisted a growing number of armed law enforcement rangers charged with keeping order in the parks. But these rangers were largely the equivalent of city beat cops; they didn’t have the time or training to solve complicated cases. In 1976, Yosemite and Olympic National Park hired the Park Service’s first criminal investigation specialists. As crime rates on public land continued to rise, other parks began to hire their own special agents who worked cases, but only cases that took place in those specific parks. In 2003, the NPS decided to put all these new special agents under one roof, enabling them to travel across the country and assist with cases wherever they were needed. And so the ISB was born.

Today, the 33 special agents travel to any National Park Service area that requests their help; I witnessed one very patient ISB agent coach a rookie ranger through the procedure for handling a stolen wallet. Depending on the complexity of the case, ISB agents may partner with other federal agents—often from the FBI—or with other law enforcement rangers. Because Park Service land is federal, prosecutions that result from ISB investigations are mostly handled through the U.S. Attorney’s office.

Last August, I traveled to Yosemite National Park to meet up with Shott’s colleague, ISB special agent Jeff Sullivan, an affable, self-deprecating, 35-year veteran of the Park Service. Sullivan has played a role in investigating nearly every major crime and mystery that’s taken place in Yosemite over the past quarter-century, which made him the ideal guide for a tour of the shadowy side of America’s fifth most visited national park. See that grassy expanse, dotted with wildflowers? That’s where park visitors discovered the skull of a still-unidentified young woman, a murder claimed by the prolific serial killer Henry Lee Lucas. That lush meadow? Once, someone found a dead bear there, its head neatly severed from its body. (The ISB sent the bear’s remains to the park’s wildlife lab in Oregon, hoping to discover clues about who’d poached it. The lab called back a few weeks later: The poacher you’re looking for is a mountain lion.)

Sullivan and I drove up to Glacier Point, where he told me about the rockslide in 1996 that killed one and injured at least 11. The dust cloud it kicked up was so massive it blocked out the sun; until Sullivan arrived on the scene, he’d been sure there would be dozens of casualties. Next to us, a bored teenager flung a water bottle into the abyss. Watching it fall seemed to cause Sullivan physical pain. He leaned in close and flashed his badge at the kid. “Don’t throw water bottles,” he said quietly.

Yosemite’s ISB headquarters are located in an imposing stone building nicknamed the Fort. It’s one of the few ISB offices that houses multiple agents, who work in a cluttered office down the hall from the park’s 20-bed jail. The walls are decorated with taxidermied deer heads, evidence tags dangling from their antlers; they’re souvenirs from a decade-old poaching case.

ISB agents are a strange breed. They require a high tolerance for time alone in the backcountry—but because solving crimes typically comes down to getting information from people, they also need social skills. “I look for people who can talk to anybody,” Sullivan told me. Each of the half-dozen agents in the office was drawn to the job for different reasons. Kristy McGee, a petite blonde wearing cowboy boots, specialized in violent crime. “I had a very chaotic childhood. I was exposed to a lot of adult-natured things—drugs, abuse,” she told me. “I found a place where I can use that to relate to people.”

Steve Kim, who has salt-and-pepper hair and a degree in wildlife ecology, told me about how he had spent the summer of 1995 living the life of a dirtbag climber, when Yosemite put out a call asking climbers to help with a death investigation. While rappelling off the east ledges of El Capitan, looking for clues, Kim discovered that ISB work suited him—“It’s probably my obsessive-compulsive tendencies”—and never looked back.

Cullen Tucker, the office’s youngest agent at age 30, was born into the business; his dad is a former deputy chief ranger at Yosemite, and his mom was one of the park’s first female investigators. Thirty years ago, the case of the dead girl in the meadow (the one whose murder was claimed by Henry Lee Lucas) had been assigned to Cullen’s mom, Kim Tucker. With very little to go on, she hadn’t been able to identify the body. “I’ve never given up thinking about it,” she told me. Sullivan recently reassigned the cold case to her son.

Over the years, Sullivan has gone undercover as a sheep hunter to infiltrate a smuggling ring that was digging up Native American burial sites. He’s done backcountry stakeouts, waiting for the marijuana planters who hide their crops among the lush growth of Whiskeytown National Recreation Area. He’s hopped on a horse and spent a week looking for poachers in the farther reaches of Yosemite. He’s interviewed Yosemite serial killer Cary Stayner and mentored young special agents navigating their way through their first thorny criminal case. He’s clearly a man who loves his job. But Sullivan freely admits that being a special agent in the Park Service can have its downsides. The work of an ISB agent is often solitary; there’s a lot of paperwork and plenty of time spent steeped in humanity’s ugliness. An ISB agent died by suicide in 2010. “It threw us all for a loop,” Sullivan said. “We worry about that a lot. It’s a stressful job.”

The winter of 2012 descended on the Rockies a few weeks after Shott’s first hike up the Deer Mountain trail. Until the spring thaw made the putative crime scene accessible again, she had to work the case’s indoor angles. In April 2014, after working with a handful of other partners, she teamed up with Jonny Grusing, a lanky FBI agent. Together, they made a classic odd-couple team. “I’m from New York. He’s from Texas,” Shott told me when I met up with the two of them last year. “I curse; he doesn’t. I drink; he doesn’t.”

“I drink!” Grusing protested. “Sometimes I have a glass of wine after work!”

Together, they interviewed people who knew the Henthorns. From the outside, the relationship seemed almost flawless. Both Harold and Toni were well-off professionals—he was an entrepreneur who raised money for churches and charities; she was an ophthalmologist from an oil-rich family. They met on a Christian dating site in 1999. At the time, Toni was in her late thirties and eager to have a child. In Harold, she believed she’d met a hardworking man who shared her faith and her desire for a family. They married quickly and had a daughter in 2005. Friends and members of the family, many of them also devout Christians, told Shott that Harold was a devoted churchgoing man.

But when Shott pulled Harold’s tax records, she discovered that he hadn’t had a job or any steady source of income for well over a decade. She couldn’t find a website for his so-called business, or any clients, or any evidence that he’d ever done any consulting work at all. His career was apparently a fabrication. So where was he going, then, when he went on business trips? Shott got a warrant for records from Harold’s cellular provider and Grusing found that his phone regularly pinged a cell tower a few miles down the road from his house. “We took a map—this is just good old-fashioned police work—and we’re like, well, what’s there?” Shott told me. They zeroed in on a shopping center called Aspen Grove. Several people had already told Shott and Grusing that Harold loved Panera, so the sandwich chain was one of their first stops when they visited the mall. Sure enough, the restaurant’s former manager recognized a photograph of Harold right away. He’d eaten there often and usually stayed until closing, typing away on his laptop. She told the agents that he was such a difficult customer that she made sure to always take his order herself. “The other Panera people were scared of him,” Grusing told me. “He didn’t feel like he had to order. He would just show up and say, ‘I’m here,’ and they would run and find Kristine.”

The fake job was the first sign that Harold’s life wasn’t as idyllic as it seemed. Another one was the insurance money. Harold had claimed that both he and Toni had $1 million life insurance policies, with any proceeds earmarked for a trust in their daughter’s name. But when Shott sent a warrant to the insurance companies, she discovered that Harold had taken out two additional $1.5 million life insurance policies on Toni, listing himself as the beneficiary or trust administrator, without her knowledge. According to the paperwork, each was supposed to replace a previous policy—insurers won’t generally allow multiple policies on one person’s life because, as an expert said in Harold’s eventual trial, people with a lot of insurance tend to die—but that original policy had never been canceled. All told, Harold had $4.5 million in life insurance policies on his wife. But that wasn’t the only insurance surprise. Shott discovered that Harold had also taken out a secret $450,000 policy on his former sister-in-law—the ex-wife of his first wife’s brother—with himself as the beneficiary.

As the investigation progressed, Harold seemed to the investigators to grow more agitated. “He’s nothing more than a Barney Fife. He probably puts out fires and writes parking tickets,” he complained, according to The Accidents. But as the investigation uncovered more about Harold’s deceptions, some friends who had initially supported him slowly began to open up to Shott. They described a deeply controlling relationship—Toni, they alleged, couldn’t talk to her parents on the phone unless Harold was also on the line. They shared stories that struck them as sinister in hindsight and that they later testified to in court—such as how, a few months before Toni’s death, the couple had been working on their cabin in Grand Lake when Harold seemed to drop a huge beam on Toni, resulting in a traumatic back injury. If I hadn’t bent down after I walked outside, the beam would have killed me, Toni had told her mother at the time.

And then there was the story of Lynn Rishell, Harold’s first wife. After receiving the anonymous notes, Shott requested the case file from the Douglas County Sheriff’s Office. She learned that in 1995, Rishell had been helping Harold change a tire on a rural stretch of road when the car slipped off the jack and crushed her. She died later in the hospital. Harold was the only witness. He received more than $600,000 in life insurance, some of it taken out just a few months before. The county sheriff ruled Rishell’s death accidental, and her family had remained close with Harold. But after Toni’s death, the sheriff reopened the investigation. “The baffling circumstances surrounding Toni’s death gave us a strong sense of déjà vu,” . “As the investigation into Toni’s death progressed, it became clear that Harold Henthorn was not the man we thought we knew, and that he had in fact been lying to us for many years.”

But the evidence against Harold was still almost entirely circumstantial, which Shott knew would make for a challenging trial. So, in the fall of 2014, once the scene was clear of deep snow, the FBI sent evidence response and special project teams to help Shott document the area for the investigation and for what they hoped would be the eventual trial. They loaded a pack of llamas with several hundred pounds of gear—water, hammocks, and the agency’s expensive laser camera—and trekked up Deer Mountain to set up camp near the crime scene.

“I think there were more FBI agents up here than there needed to be, just because they all wanted to come camp,” Shott told me. Some, she said, had never spent the night outside before. (“How do we eat?” Shott recalls one of them asking.) During the day, they used the laser camera to create a 3D model of the scene. But the computerized recreation looked like an image from a video game; it didn’t have any of the rugged drama of the actual location. Shott worried that a jury wouldn’t understand just how unlikely Harold Henthorn’s story was.

In November 2014, after a two-year investigation that was still ongoing, Henthorn was indicted on first-degree murder charges. He was taken into custody, and his daughter was sent to live with longtime family friends.

Shott began to prepare for what she knew would be a high-profile trial. “This is the kind of case you wake up in the middle of the night obsessing about. It’s all-consuming,” she told me. “How do we prove it? And how do we boil it down to a three-week trial?” She consulted with a forensic anthropologist to see if there was any way to determine from Toni’s injuries whether she’d fallen or been pushed. What if they tossed a dead pig off the cliff so they could study its injuries?��(“A pig we didn’t like,” Grusing joked. “Not a nice pig.”) But the anthropologist didn’t think it would be helpful. Instead, Shott hiked the Deer Mountain trail over and over again—with her FBI partners, with the federal prosecutors assigned to the case, on her own. She took three trips using GoPros to gain new perspectives. She got a special permit for an operator to fly a drone in the park to further document the site. On one visit, the winds were so strong that she and another park ranger with her had to turn back for fear that they’d get blown off the ledge. She couldn’t shake the gnawing worry that she’d missed something, some crucial clue, some path through the woods that the defense would present at trial, blindsiding her. Overall, Shott made at least 15 trips over three years, picking her way up and down the scree slopes, trying to imagine what Toni had been thinking and feeling that day. She never once made it to the summit.

Harold Henthorn went on trial for Toni’s murder in September 2015 at the federal courthouse in downtown Denver. There was still no physical evidence that could establish that Toni was pushed, so the prosecution’s case hinged on proving to the jury that Harold was a man with a secret life, who was financially dependent on the wife he’d been lying to for years.

Shott took the stand toward the end of the trial. She’d testified a half-dozen times before, but this was her first murder trial, and it felt different, heavier. The jury had already heard most of the state’s case against Harold by this point. Shott laid out various pieces of the puzzle: her assessment of the scene, the time stamps on the digital photographs Harold took, and the text messages he sent. The jury was allowed to pose questions, and they learned that another place Harold claimed to have had “romantic time” was on the rocky crow’s nest. One jury member wanted clarification: Really? There? Yes, Shott said.

On September 21, the verdict came back: guilty of first-degree murder. As Harold was led out of the courtroom, Lynn Rishell’s brother, Eric, , “Goodbye, Harold!”

The following year, then–Attorney General Loretta Lynch presented Shott and the other key players in the case with a , the second-highest honor given by the Justice Department for employee performance. “Due to their dedication, painstaking work and powerful trial presentation, the recipients did what many thought was impossible by obtaining a conviction in this difficult and wholly circumstantial case,” the citation noted.

By the time the award was presented, Shott was back to her regular ISB work, sifting through hard drives and recovering deleted files. One child pornography case that took place in Grand Canyon National Park was particularly soul-demolishing; something in her gave way and it became clear that she could not look at one more image of a child being violated. In January 2017, she left the ISB for a new job as deputy chief of the National Park Service’s Office of Professional Responsibility.

In August 2017, though, Shott agreed to return to her old stomping grounds to hike the Deer Mountain trail with me. FBI agent Grusing came along, too, and so did two of the assistant U.S. attorneys who prosecuted the case. It was something of a valedictory hike; on July 26, a federal appeals court affirmed Harold’s conviction. Later, in 2018, the U.S. Supreme Court would decline to hear Harold’s appeal for a new trial, meaning that, barring some extraordinary circumstance, he’ll be in federal prison for the rest of his life.

We were all breathing hard by the time we turned off the main trail and headed into the woods. We picked our way through the scrub, passing the flat spot where the FBI agents had camped out, and then the lunch spot, where the views Toni and Harold had enjoyed were spectacular. Grusing played us all a voicemail he’d received the day Harold Henthorn was found guilty, left by then–FBI Director James Comey: “Hey, Jonathan, this is Director Comey calling…I wanted to thank you for an extraordinary piece of work, so extraordinary it makes me proud to be working at the FBI, because we’re doing that kind of quality work.”

“Oh my God, that’s so cool,” Shott said. “I thought you were bullshitting. That was really Comey.”

Then we scrambled down the slope, and I found myself in the narrow space where Toni Henthorn had stood five years earlier. “So this is the fall spot,” Shott said briskly. “Well, she falls into a tree, and there’s blood and hair in the tree, and the branches are broken. Be really careful here,” she warned me. I’ve never been particularly afraid of heights, but I could bring myself to peek over the edge only briefly; I couldn’t stop imagining what it might’ve felt like when Toni toppled over the edge. It made my head spin.

It was a relief when we reversed course and began to make our way back to the main trail. Shott started telling me about how, on some of her trips out to the site, she’d think about what she might have asked Toni: You’re a smart, beautiful, accomplished woman, she’d imagine herself saying, and this man was such a liar, such a bully. You must have seen that. Why didn’t you leave? She began answering her own questions—they had a daughter; Toni already had one failed marriage; Harold was supremely manipulative—but then she stopped herself. Too much speculation about things you’ll never know can drive you crazy, as any ISB agent could probably tell you. But as we picked our way among the fallen trees, away from the forlorn spot where a man had shoved his wife off a cliff, I understood why someone like Shott might keep asking. When your job takes you deep into the woods, of course you’re always looking for a path that might lead you out.