On September 12, 2025, a maintenance worker named Ray Diaz opened the door of an abandoned pump house in a remote corner of Yellowstone National Park and found a pile of old tarps in the corner. Then it moved. A man was hiding there, severely emaciated, covered in dirt and dressed in tattered scraps of fabric that included what looked like parts of a uniform. When park rangers arrived, the man identified himself as Marcus Herrell, a 32-year-old geology teacher who had vanished in the park four years earlier.
His body told a different story than the one he tried to tell. He kept repeating a strange phrase: “There’s no steam. They’re cold where he keeps them. The geysers that don’t steam.
”
Marcus Herrell had entered Yellowstone on June 17, 2021, planning a week-long solo camping trip through the park’s less traveled northwestern quadrant. A resident of Idaho Falls and an experienced outdoorsman, he had visited the park dozens of times. His permit showed he intended to camp at four backcountry sites over six nights, moving roughly seven miles each day. Surveillance footage captured him at the backcountry office that morning wearing a red jacket and carrying a large green backpack.
At 9:47 a. m. , he sent a text to his sister Sarah: “Just got my permit. Heading out now.
Should have cell service again in a week. Love you. ” It was the last confirmed communication from him. His truck was later recorded entering the parking lot at Norris Geyser Basin, where his hike was believed to have begun.
When he failed to return home on June 24, Sarah reported him missing. Rangers found his locked truck with no signs of disturbance, but his phone, wallet, and itinerary were not inside. After checking his planned campsites with no success, the park activated a full search and rescue operation. Over 80 people took part, including rangers, volunteers, dog teams, and helicopters.
On June 28, searchers found his backpack about two miles from his first designated campsite, carefully placed against a tree near a small unnamed thermal area. His tent, sleeping bag, cooking equipment, and food were inside, but his water filter, first aid kit, and emergency satellite beacon were missing. Tracking dogs followed a scent trail northwest for roughly 800 yards before losing it in rocky terrain. After three weeks without further signs, the active search was suspended on July 15.
Marcus Herrell was declared missing, presumed dead. Four years later, his discovery in the pump house changed everything. Hospitalized at Eastern Idaho Regional Medical Center, he weighed 112 pounds, about 70 pounds less than when he disappeared. Medical records showed severe malnutrition, vitamin D deficiency, multiple healed fractures in his right arm and two ribs, and circular scarring around both ankles and wrists.
Doctor Elena Reyes noted that the vitamin D deficiency suggested long-term absence of sun exposure, and that the uniform pattern of scarring indicated prolonged restraint with man-made materials. His muscle atrophy suggested restricted movement over an extended period. When Marcus first began to speak clearly, he claimed he had gotten lost after leaving the trail to examine a geological formation, injured his ankle, wandered for days, found the pump house, and lived there foraging for four years. He said he was too ashamed to seek help.
Investigator Thomas Werner found significant inconsistencies. The vitamin D deficiency contradicted the claim of regular outdoor foraging. The muscle atrophy did not match someone moving through wilderness. The callous patterns on his hands did not match survival activities.
And the pump house had been inspected 18 months earlier with no evidence of habitation. When Werner pressed him, Marcus became agitated and repeated, “You don’t understand. I had to stay there. I had to say this.
He’ll know if I don’t. ”
Federal investigators joined the case, and FBI special agent Diane Carter, who had experience with long-term captivity cases, took over the interviews. She focused on building trust rather than confrontation. On his fifth day in the hospital, Marcus handed her a small brass token he had hidden in his cheek, a disc the size of a quarter stamped with an image of a geyser-like formation and the number seven.
“He gives these when you’ve been good,” Marcus said. “I was allowed to keep this one. ” Forensic analysis showed the disc was made of brass commonly used in plumbing fixtures, engraved with precision tools, and covered with trace particles matching mineral deposits found near Yellowstone’s thermal features. While reviewing maintenance records, investigators discovered an abandoned research facility used during the 1970s to monitor thermal activity, officially closed in 1985 but showing consistent electrical usage over the past five years.
Located about 15 miles from where Marcus was found, it sat above an area of geothermal activity where thermal water remained below the surface, never breaking through as springs or geysers. As one investigator noted, these were exactly the geysers that didn’t steam. Inside, what had once been research labs had been converted into living quarters and confined spaces. Three storage rooms had been transformed into cells, each with a mattress, a bucket, and a reinforced door with a locking mechanism that could only be operated from outside.
In one cell, investigators found Marcus’s driver’s license and the emergency satellite beacon missing from his backpack. A workshop contained metalworking tools and seven distinct token designs, with numbered molds ranging from one to twelve. Marcus eventually revealed that on his first day hiking, he had encountered a man posing as a park geologist. The man wore a credible uniform, knew everything about geology, and invited Marcus to see a special research station monitoring unique thermal features.
Once inside, Marcus was drugged and woke restrained in one of the cells. The man told him he was lucky, that being educated meant he could appreciate the work, “not like the others. ” Over time, Marcus described a captor he knew only as “the supervisor,” a man conducting his own obsessive research on the geothermal system and using captives as labor and audience. The token system was central to control.
Compliance earned tokens that could be exchanged for basic comforts like extra food, a blanket, or time outside the cell. Resistance meant isolation, food restriction, or physical abuse. The investigation identified the supervisor as Howard Merritt, a geologist employed by the National Park Service at the research facility between 1980 and 1984, who had been vehemently opposed to its closure. After dismissal, he had bounced between universities before promoting fringe theories about Yellowstone’s thermal activity and dropping out of academic circles.
He had purchased a small cabin outside West Yellowstone, Montana, in 1998, and utility records showed patterns suggesting he spent significant time elsewhere. At the facility, investigators found personal effects belonging to at least three other individuals reported missing in Yellowstone between 2017 and 2024, along with journals containing meticulous observational notes on thermal activity and on captives identified only by number. The writing suggested Merritt believed the presence of captives affected the thermal activity in some way. Marcus’s testimony revealed a methodical operation.
Merritt targeted individuals with scientific backgrounds or those traveling alone, approachable through a convincing persona. Captives were kept separate, and the token system prevented solidarity. Marcus described hearing sounds of struggle followed by long absences, and Merritt returning with items belonging to the missing person as warnings. “They failed to appreciate the system,” Merritt would say, showing their watch or glasses.
Marcus believed he buried them somewhere near the thermal features. Investigators identified at least four other likely captives over the past eight years, and believed at least three may have died. On October 2, 2025, a hospital security guard intercepted a man attempting to enter the secure ward where Marcus was being treated. The man presented identification as a federal investigator, but when challenged, fled.
Surveillance footage matched Howard Merritt’s description. On October 7, police located his cabin and set up surveillance. After 36 hours, a tactical team entered, finding maps of Yellowstone marked with thermal areas, uniform parts, and equipment for creating identification badges, but Merritt was gone. A receipt showed he had purchased camping supplies in Bozeman two days earlier.
On October 12, a park visitor reported a man living rough near a little-visited thermal area in the park’s northern section. Rangers found Howard Merritt at a makeshift campsite about three miles from the abandoned research facility. He attempted to flee but was quickly apprehended. During interrogation, Merritt spoke at length about signals in temperature variations and patterns that only became clear through constant controlled observation.
He referred to his captives as observers or participants, claiming they had volunteered once they understood the importance. When confronted with evidence of force and restraint, he dismissed it as necessary protocols. Asked about the missing individuals, he called them failed observers who couldn’t adapt to the requirements, and refused to clarify their fate. Merritt was charged with kidnapping, false imprisonment, assault, and impersonating a federal employee.
In March 2026, he went to trial. Evidence included the modified facility, restraint devices, the token system, his journals, and testimony from Marcus. A psychological evaluation determined that while Merritt suffered from delusional disorder, he remained competent to stand trial. The jury deliberated less than six hours before returning a guilty verdict on all charges.
In May 2026, he was sentenced to multiple life terms without parole. For Marcus Herrell, the conviction brought legal closure but limited psychological resolution. He now lives in a different state under family care, receiving treatment for PTSD, anxiety, and persistent physical issues from long-term malnutrition and confinement. He still exhibits hypervigilance around locked doors and windows.
The search for the remains of other victims continues, using ground penetrating radar near the thermal features where Merritt focused his activities. The National Park Service added security measures for monitoring abandoned structures and implemented new protocols for verifying the identity of all personnel wearing park uniforms. Marcus still keeps the brass token with the number seven in a locked box. He sometimes holds it during therapy sessions when discussing difficult memories.
When asked about his future plans, he said simply, “I stay where I can see roads and people. I keep all the doors locked. I check them three times before sleeping. ” The abandoned research facility has since been demolished, its location unmarked on any tourist map.
But in the northern section of the park, there is an area where the ground is warm to the touch, though no water breaks the surface. The geysers that don’t steam remain active beneath the earth, monitored now by proper scientific equipment and professional staff.