In 1973, eight Americans attempted to summit Aconcagua, the highest mountain in the western and southern hemispheres. Only six returned. Sounds like the notoriously deadly mountain collected two more victims. Or maybe that’s just what the killer wants you to think. Conspiracy Theories is on Instagram @theconspiracypod and TikTok @conspiracy.pod! Follow us to keep up with the show and get behind-the-scenes updates from Carter and the team. Learn more about your ad choices. Visit podcastchoices.com/adchoices
Chapter 1: What happened during the 1973 Aconcagua climbing expedition?
Due to the nature of today's episode, listener discretion is advised. This episode includes discussions of graphic body horror and death. Consider this when deciding how and when you'll listen. It's 1973, a hotel in Mendoza, Argentina. energy is high. Eight Americans are staying there, but just for the night.
In the morning, they'll start a trek all the way to the summit of Aconcagua, the tallest mountain in the Western Hemisphere. That's the plan, anyway. A local reporter, Rafael Moran, is there documenting the group alongside a photographer. When the New York Times interviewed Moran 50 years later, he told them he didn't cover every bunch of foreigners that showed up to conquer the mountain.
But at the time, this one feels special. There's a NASA engineer, a police officer, a doctor, a lawyer, and even a woman, which is remarkable for the time period. plus the parties attempting the difficult Polish route, which requires them to scale 2,000 nearly vertical feet up a massive glacier to reach the summit. Only four other groups have managed it since 1934.
As Moran interviews everyone, something feels off. These people should feel like a team. They're about to embark on a difficult, dangerous journey, but there's no sense of solidarity. In fact, many of them hardly know each other. They're from different cities and some are just meeting for the first time. Moran pulls the photographer aside and instructs him to get individual shots of everyone.
It'll be convenient to have current photos on file. If anyone doesn't make it off the mountain. Welcome to Conspiracy Theories, a Spotify podcast. I'm Carter Roy. You can find us here every Wednesday. Today, we're covering two mysterious deaths near the summit of Aconcagua. Officially, they were accidents.
But ever since the bodies were recovered, theories have flown about murder on the mountaintop. Be sure to check us out on Instagram, at The Conspiracy Pod, and we would love to hear from you. So if you're listening on the Spotify app, swipe up and give us your thoughts. Stay with us.
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Chapter 2: Who were the climbers and what were their backgrounds?
In 1973, the American climbers needed more supplies than they could carry at once, so their ascent was actually a maddening logistical nightmare of shuttling equipment up the mountain, then turning around to go down for the next load, for days on end. And then there's the elevation. Aconcagua is the highest mountain outside of Asia. Base camp is at roughly 13,500 feet.
That's just a thousand feet shy of the highest point in the continental United States. And this is the starting point for the Polish route. From there, it's another 8,000 feet up to the summit at around 22,800 feet, over four miles above sea level. The physical effort of getting to that elevation is no joke, but that's not why it's hard.
Add to this the fact that the human body doesn't function well at high altitudes because the air doesn't have as much oxygen. And the higher you go, the less oxygen there is. Take it from me, I went to Everest Base Camp, climbed Kalapatar. At 16,000 feet, every breath feels like a hammer in your head. It is hard. That low oxygen forces climbers to breathe deeper and faster.
The body wants to protect the brain so blood vessels in the head dilate. That keeps everything firing up there, but the expanded vessels increase pressure. That means headaches. Severe ones, as I said. And those are just the basic symptoms of high altitude, called altitude sickness, that pretty much everyone experiences. it can get a lot worse.
Fatigue, dizziness, sleep issues, vomiting, loss of coordination, mental fog, heart palpitations, and all that is considered mild. When altitude sickness is severe, fluid can accumulate around the lungs or lead to swelling of the brain. At that point, you better get to a lower altitude fast or you're dead. So climbing Aconcagua is not a walk in the park.
Today, climbers mitigate the risks by ascending with GPS trackers and radios. Some bring supplemental oxygen or take altitude sickness medication. And there are helicopter evacuations and rangers on standby for rescue efforts. But in 1973, mountaineers had none of those safety nets. If you needed help, it had to come from the people climbing beside you.
By the time the group reaches their highest and final camp at 19,400 feet, they're well acquainted with the risks of their climb. Altitude sickness has already forced three of the eight American climbers back down to lower elevations.
The remaining climbers are John Cooper, the NASA engineer, Janet Johnson, a teacher and the only woman in the group, Bill Zeller, a police officer, Arnold McMillan, a farmer, and Jim Petroski, a psychiatrist. They're accompanied by Miguel Alfonso, their guide. It's been a hard journey to get this far, and it does not seem like the hardship fostered any team spirit. Alfonso is highly experienced.
He's summited via this difficult Polish route before, but the group doesn't defer to him as the leader. It seems like they treat him more like the hired help, there to give advice or keep his mouth shut when needed. There's grumbling among the ranks too. Hooper complains in his journal that Johnson isn't pulling her weight.
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Chapter 3: What challenges did the climbers face on Aconcagua?
To him, it seems like she's there just to get to the summit, and she's happy to let everyone else do the work. But he also cops to carrying less weight than Zeller. The altitude makes everything more difficult. That reporter back in Mendoza wasn't the only one who thought these climbers were only looking out for themselves.
Despite the dysfunction, the remaining group is now just a one-day climb from the summit, conditions look perfect. Everyone is ready to make a final push up the steep glacier to the top. But as everyone gets suited up, Petroski suddenly can't figure out his crampons, his specialized ice shoes. He's disoriented.
They all agree that he's showing symptoms of altitude sickness, perhaps even that deadly version that causes the brain to swell. He needs to get to a lower elevation pronto, and he can't do it alone. Alfonso, the guide, accompanies him down the mountain. The remaining four climbers have a decision to make. Are they going to continue climbing without a guide?
Cooper, McMillan, Zeller, and Johnson don't know each other well, and none of them has ever been at this elevation before. The smart choice is probably to descend. That's certainly safer. But they've come all the way around the world and toughed it out on an unforgiving mountain for eight days. Now the sun is shining. They are so close. They all agree. There's no turning back now.
It's important to note that from here on out, our story comes entirely from the memories of the survivors. Their version of the story is the only one we have. The group decides to lighten their loads to hopefully accelerate their progress. They leave their packs behind, carrying just their ice axes and a few essentials. For Johnson, that includes her camera. She takes photos as they climb.
But a few hours later, it's starting to get dark. They'd hoped to scale the glacier in one day, but they have roughly another thousand feet to climb with none of their gear. They're forced to dig an ice cave to sleep in. It's claustrophobic. After a few hours, Johnson and Zeller can't stand it. They give up on sleep and wait out the night at the mouth of the ice cave.
Powder blowing down from overhead almost seals the cave's entrance. Johnson digs Cooper and McMillan out at first light. Cooper spent most of the night with his legs buried in the snow. He's had it. He tells the group he's returning to camp. As best anyone can tell, Cooper is of sound mind and capable of getting down on his own. It's about a 1,000-foot descent, which is significant.
But to the climbers who had been going up and down that distance every day, it didn't seem far at all. With Cooper gone, only Zeller, McMillan, and Johnson remain, and they all agree, get to the top. So they continue, without gear, and at this point, without any food. They start off optimistic. The weather is clear, but they begin to sink into the fine powder on the glacier.
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Chapter 4: How did altitude sickness affect the climbers?
Soon, they're waist deep in the snow. Zeller and McMillan take turns plowing the trail, 25 steps at a time. Johnson trails behind them. They're on a ridge, and it looks like the top is in sight. Although the climb is grueling, it seems straightforward. But nothing is straightforward at 20,000 feet. The summit becomes a cruel mirage.
Multiple times they're sure it's just a few steps away, only for them to see another ridge above them. Their bodies are working at the absolute limit. This time, when the sun goes down, they just keep climbing. They're all exhausted by the time the true summit finally comes into view. They're having to rest after each step. Just another 200 feet now, and they'll reach the top.
But at the rate they're going, that distance will take hours. During this process, everyone starts seeing strange things. Zeller notices a construction truck parked on the mountain. Must be here to do some work, he thinks, before realizing that is positively ludicrous. There is no construction truck. He's hallucinating.
That realization brings Zeller back to Earth, and just about the only thing he knows is real, his companions. Macmillan is right beside him, but it's just the two of them. Johnson is gone. Argentina, 1973. Three mountain climbers are near the top of the tallest peak in the western and southern hemispheres in the middle of the night. One of them is missing.
The two men, Zeller and McMillan, turn on a flashlight. It's almost out of battery. They call out for Johnson, but their voices probably don't reach any farther than the flashlight's weak beam. They're surrounded by vast, dark wilderness. They descend, retracing the trail they plowed through the snow. Finally, they hear a soft voice responding to their calls.
They find Johnson lying on the snow about a hundred feet off the trail. She's not in her right mind. She begs the men, quote, just let me lay here and die. but they pull her to her feet instead. The trio trudges down the mountain. Despite all their efforts, none of them make it all the way to the top. There are different versions of what happened next.
According to one survivor, they all sleep exposed on the glacier, too exhausted to dig an ice cave. The other says he leaves the other two and sleeps alone. As he drifts off to sleep, Zeller hears voices. Perhaps he assumes their rescuers can't be too far away. It wasn't until Zeller got off the mountain that he learned help was never coming. These voices were more hallucinations.
Regardless of what really happened overnight, everyone reconvenes the next morning. Johnson is in bad shape. Her hands are swollen and discolored. She refuses to stand. But again, the men rouse her and tie her between them so they can help her stay upright. Eventually, they get down to the ice cave where they separated from Cooper.
Some of their abandoned equipment is still there, including a flare gun. McMillan fires it. No one below sees it or hears it. For lack of a better alternative, the group decides that McMillan should go down to get help. They're about 2,000 feet above camp, which means food, tents, and sleeping bags, and hopefully someone else who can help them get off this mountain. McMillan departs, alone.
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Chapter 5: What decisions did the remaining climbers make as they approached the summit?
She'll follow him down as soon as she catches her breath. Zeller makes it down to camp and finds McMillan already asleep in one of the collapsed tents. He climbs into a sleeping bag beside him and passes out. It's their first proper rest in three days. Zeller and McMillan sleep until the next morning. They emerge from the tent but can't find any sign of Johnson.
Zeller and McMillan check the landscape outside, but it's hard to see. The sun glares off the ice, and Zeller doesn't have his sunglasses, having broken them in the fall. Everything is blurry and too bright. Zeller's worried. He doesn't think Johnson could have survived another night out in the elements.
The men decide the best thing to do is to descend farther and see if they can find others to help search for Johnson. Down at base camp, the other members of the party have been watching the climbers through binoculars. Worry spread through camp when they could only spot three of the four hikers, and then only two.
When it was clear the climbers were descending from high camp, Alfonso, the guide, and the youngest member of the group, John Shelton, hurry up the mountain to meet Zeller and McMillan. Shelton feels grim as he confirms it with his own eyes. Only two of his four companions are here. Zeller and McMillan spend two days recovering in sleeping bags at base camp,
In addition to exhaustion and altitude-related symptoms, McMillan has a black eye from his fall. Zeller looks grotesque. His forehead is black from exposure and blood vessels are ruptured in his eyes. Alfonso heads all the way down the mountain for more help. Word of Cooper's death and Johnson's disappearance spreads quickly.
It's a sensational story and the media jumps on it before an investigation can get underway. So initial news coverage is heavy on speculation. A paper in Cooper's hometown publishes that he's presumably dead after falling off the top of the mountain during a snowstorm and landing in a crevasse.
As soon as the seven survivors reach the foot of the mountain, Argentine investigators intercept them for questioning. They're all essential witnesses in a potential manslaughter case. Some journalists find the climbers' accounts hazy and inconsistent. the US State Department has a similar experience.
In the New York Times extensive reporting on the 50th anniversary of the climb, they noted plenty of inconsistencies in public interviews and coverage at the time. Some are small. For example, when Zeller and McMillan found Johnson lying off trail near the summit, Zeller says that he used rope to help her off the ground, and McMillan says that Zeller grabbed her arm.
but some discrepancies seem more significant. Zeller thinks they all camped together after the failed summit attempt, but McMillan says he spent the night alone. This inconsistency on a really basic fact exposes just how muddled Zeller and McMillan's memories are.
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Chapter 6: What were the circumstances surrounding the disappearance of Janet Johnson?
Carmi Defoe, the climber who organized the expedition, and a lawyer, tells the State Department that they shouldn't put much stock in any of the survivors' statements. The altitude made them all hallucinate. It gave the whole expedition a dreamlike quality. The Argentine police officer running the investigation comes to a similar conclusion.
So in his mind, the answer to this case can't come from witness statements. It has to come from hard evidence, the victim's bodies. At this point, it seems most everyone assumes Johnson died somewhere on the mountain too. The medical examiners aren't exactly prepared to summit Aconcagua, and retrieving the remains of John Cooper and Janet Johnson is not a straightforward task.
Authorities have no idea where Johnson's body might be, and only a vague sense of Cooper's location. Even once they are located, it will be another big feat to bring the remains down the mountain. Remember, experienced hikers fell climbing down, and they weren't hauling extra weight. On top of all that, conditions are not favorable for a retrieval mission right now.
Aconcagua is in Argentina, so December to February is the warm season. They'll have to wait until the end of the year to make another attempt. Back in the States, Janet Johnson and John Cooper's families process their loss. Cooper's family holds a memorial and anxiously awaits his remains. And his father learns Spanish so that he can better follow updates from Argentina.
Johnson's family relays her wish to Argentine authorities that she be buried near the mountain. Her mother reads every news report she can and carefully fixes each misspelling of her daughter's name by hand. When she comes across a quote from her daughter asking to die, she crosses it out.
Before 1973 comes to an end, a team heads up Aconcagua with the equipment they'll need to bring down a human body. Miguel Alfonso, the guide on the ill-fated expedition, goes along. They find Cooper on a flat surface, legs straight. His hands are bare, laid on his belly. He's missing a crampon and his ice axe. Alfonso was surprised to find Cooper stretched out.
He remembered that Zeller said Cooper was frozen into a crouched position. The team carefully photographs everything before excavating the body onto a sled. They also search for Johnson. But they can't find her. A medical examiner performs Cooper's autopsy down in Mendoza. His face is beat up and frozen in an expression of terror.
Once his arms thaw out, the medical examiner moves them and finds another wound in Cooper's abdomen, under where his hands had been. It's a deep, round hole that penetrates all the way to Cooper's spine. It was actively bleeding when he died. When the autopsy is complete, the judge opts to keep its contents under wraps. He only releases two things. The cause of death and a short statement.
Cooper's official cause of death? Cranial contusions. Cooper did not freeze to death. He didn't bleed to death. Something hit him on the head hard enough to kill him. As for what? Well, the judge makes a statement. He can't make any determination in the case until he has Janet Johnson's body.
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Chapter 7: How did the media cover the aftermath of the expedition?
It's hard to imagine anyone pulling that off. It would have been a lot easier for someone who was already with the group. Zeller and McMillan aren't clear-cut suspects. There's really not a viable motive for them to kill Cooper or Johnson, but their explanation of what happened doesn't totally add up. There are many inconsistencies in their stories.
When exactly did they separate and come back together? When did each of them come across Cooper's body and what state was it in? And how exactly did Zeller leave things with Johnson? Like I said before, some of this can definitely be chalked up to the mind scrambling effects of high altitude. But there are a few hints that Zeller and McMillan might have known more than they shared publicly.
You'll remember that Carmi Defoe, the man who organized the trip, downplayed the group's recollections to the U.S. State Department. But then after Defoe returned to the States, he helped organize a secret meeting of his climbing club and summoned McMillan and Zeller to it. The goal of the gathering was to, quote, learn the straight of things.
The meeting resulted in a timeline that went into the climbing club records and seems to have informed Zeller and McMillan's later interviews. It ends with the conclusion that Cooper and Johnson probably died from complications from altitude sickness, which we now know they did not.
There was also a curious letter from Lauren McIntyre, one of the people who recovered Cooper's remains to Cooper's widow. He encouraged her to get in touch with Zeller and McMillan because he suspected that the men may have adjusted the truth to make it easier for their consciences to deal with. Then there's the physical evidence on the two survivors.
Both Zeller and McMillan reported falling during their descent, but neither man had the broken bones, scrapes, or bruises experts expect to see from a fall. McMillan only received a black eye, and Zeller cut up his face and broke his sunglasses. Naturally, that's led to speculation about Zeller and McMillan's actions on the mountain. Why they survived and Cooper and Johnson did not.
To be clear, they were never suspected killers. But let's talk about how whatever might have happened between the climbers could still fall under the umbrella of accidental deaths. It's not clear if McMillan was feeling the physical effects of the altitude, but Zeller, Cooper, and Johnson all had bodily symptoms at some point during their summit attempt.
In addition to all those symptoms, advanced altitude sickness can also cause unpredictable changes in mental status. We also know that Zeller and McMillan experienced psychological symptoms, visual and auditory hallucinations. Back in the 70s, experts attributed these wild psychological experiences to altitude sickness.
But in recent years, some scientists isolated them into a separate potential diagnosis. high altitude psychosis. Psychosis isn't just hallucinations, it's also delusions, believing something that isn't true. The new diagnosis came about in part because a researcher experienced it himself while at roughly 26,000 feet. He was exhausted after a nighttime summit and desperate for a place to rest.
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Chapter 8: What inconsistencies emerged in the survivors' accounts?
Not how she died, but proof that she did climb Aconcagua. Thank you for listening to Conspiracy Theories, a Spotify podcast. We're here with a new episode every Wednesday. Be sure to check us out on Instagram at The Conspiracy Pod. If you're listening on the Spotify app, swipe up and give us your thoughts. Or email us at conspiracystories at spotify.com.
Amongst the many sources we used, we found reporting by the New York Times extremely helpful to our research. They published a comprehensive report in 2023 led by John Branch, with additional reporting by Pablo Betancourt and Nicolas Garcia. Until next time, remember, the truth isn't always the best story. And the official story isn't always the truth.
This episode was written and researched by Hannah McIntosh, edited by Mickey Taylor and Maggie Admire, fact-checked by Laurie Siegel, and sound designed by Kelly Geary. Our head of programming is Julian Boisreau. Our head of production is Nick Johnson, and Spencer Howard is our post-production supervisor. I'm your host, Carter Roy.