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Mark Polymeropoulos always thought that if his job as a CIA agent ever caught up with him, it would be under enemy fire.
I was dodging rockets from the Taliban and al-Qaeda. You know, I've been in a lot of kind of hairy situations.
He's an old CIA hand, a kind of silverback guerrilla version of Adam, the field agent who set off a crisis in Havana after reporting a strange sound and pressure in his bedroom.
So in December 2017, I was the deputy operations chief for the CIA's Europe and Eurasia Mission Center, which is the equivalent of a one-star general in the military.
He'd never been to Moscow. He set off on a 10-day area familiarization trip to meet with his Russian counterparts.
Because, you know, even in the darkest days of the Cold War, you know, the CIA and the KGB had, you know, had ties. You always want to have these open ties.
But he says that ahead of the trip, the Russians seemed unsure about granting him a visa.
And, of course, our response is, you know, this is not an operational trip. We're not coming to spy on anybody.
They're a bit cranky about it, and they finally acquiesced. But looking back, perhaps that was something I should have listened to a bit more closely.
He sat in on a few meetings, tried out a Russian McDonald's, and took a selfie outside the Kremlin, two days of what he called a pleasantly boring business trip.
And then, on the third night...
I don't remember hearing anything, but something caused me to wake up, and I was in a considerable amount of distress.
I thought it was food poisoning, because I could barely stand up. The room was just spinning wildly.
He dosed up on painkillers and completed the trip.
But he now had a migraine that didn't let up and found himself getting dizzy all the time.
When he got back to the U.S., he went to see medical staff at headquarters.
It seemed to me that it was similar to some of the symptoms I'd heard about from our colleagues at the embassy in Havana.
The Havana crisis was almost a year old, and it had been headline news for four months.
And, as best we can tell, the CIA were taking Havana syndrome seriously.
They had closed up shop in Cuba entirely, and secured care for affected agents at a state-of-the-art facility at the University of Pennsylvania.
But Polymeropolis says that the CIA medical staff refused to send him there.
They put me some rudimentary tests, and they just kept saying no.
He doesn't think the medical staff had any agenda.
He says they just weren't willing to accept that there might be a link.
Why not send you to the place that's studying this kind of thing at the moment, and they can make that decision?
Well, that's the biggest question, Sam.
At the end of the day, the title of my story, I'm joking, there's no book, but all I wanted to do was see a doctor.
In the end, he would be counted among the Havana syndrome victims, and would become perhaps the most outspoken of all of them.
But in those early days, he felt not just like he had fallen through the cracks, but that the CIA had missed something major.
That what was affecting a small cluster of secretive spies in Cuba may just be the tip of the spear.
And that Havana syndrome was now surfacing halfway across the world.
From BBC Radio 4, this is Havana Helmet Club.
I'm Jennifer Ford.
I'm Sam Bungie, and this is Episode 6, The Thing.
At the Perlman School of Medicine, at the University of Pennsylvania, security is tight.
I had a handler with me at all times for the two days I was there.
It's where they developed the technology behind some of the COVID vaccines.
And somewhere in this complex of buildings, there are computers holding the data about the brains of the 22 patients from Cuba, known as the Havana cohort.
Back in late 2017, these American spies and diplomats were spending every day being tested at a clinic here called the Center for Brain Injury and Repair.
The government had been looking for somewhere to bring the patients that could handle this kind of issue.
The CIA reached out to Doug Smith.
It was a holiday weekend in the summer, and I get this very strange email.
Professor Smith, who has a bushy moustache that reminds me of a 1970s American TV news anchor, had been sceptical at first.
I said, did they, you know, hit their heads? No.
They just had some kind of a directional phenomenon.
They felt something, a force, something coming from a certain direction, and they were looking for my input.
Smith had his team of doctors examine the patients, each running their own balance and cognitive tests, all without talking to each other.
Then, sometime in about mid-September, just down the hall here, we had the reveal.
One after another, all the clinicians agreed that their experience with the patients was there was definitely something neurological there.
So, a second group of doctors came to tell the patients that they were showing signs of brain injury.
And they were actually very grateful.
I mean, if you, you know, you think it's kind of odd, you say, we think something was damaged in your brain.
We don't have direct evidence, but these changes suggest that there was something changed in the conductivity of your brain.
And I think that they really appreciated that.
Still, Smith told us he was clear with the patients that he didn't have all the answers.
The problem with concussion is that it's not really a diagnosis as it is right now.
So, concussion is really an opinion.
There isn't a blood test or a scan to objectively prove a concussion.
Also, the term concussion itself doesn't tell you what led to your injury.
A definition of diagnosis is that the name also embodies or implies the underlying cause.
So, there are over 30 official definitions of what it is, but they only ascribe to the symptoms.
Smith says the patients had a sense of humour about it.
They called the disorder immaculate concussion.
I call it concussion without a concussion.
And I said, we're really at the starting line.
You know, by the time I showed up in Penn, I was averaging two to three hours of sleep a night broken.
I was a zombie.
Adam, patient zero of the health crisis in Havana, he says the rehab at UPenn was helping him to turn a corner.
He rented an apartment in the city and went in and out of the clinic along with the other patients.
He began to feel like he was on track.
There was one troubling development.
It began when he got the feeling that he was being trailed, coming in and out of UPenn.
There was someone photographing me and then following me.
It's like out of a movie, running through the city, chasing after this car to get the license plate and look at the driver.
Some days he was convinced his car was being followed.
Other times he says he would return home, certain that his stuff had been rearranged while he was out.
Once Adam showed me a photograph that he took during this time of two men in a cafe.
He says they didn't order anything.
They just sat themselves next to Adam and his friend, speaking in Russian and paying him close attention.
All I saw in the photo was two burly fellows looking awkwardly at the camera.
But Adam has a different way of reading the world from me.
He once operated in a realm where people really do follow you and where you can call a friend in the feds and run a license plate.
We can't do that and we weren't able to confirm his surveillance claims.
But Adam says that's what drove him out of Philadelphia.
I left Penn early because the harassment got so bad and that it was just taking a toll on me mentally.
Adam had a theory as to why his attackers would still be interested in him and his treatment at UPenn.
Are my medical files interesting to them? Yeah, sure.
You're going to try and sell it to other countries and now you've got the results showing this is what happened and, oh, by the way, we closed down the US embassy.
You want to buy one?
You can't get any better marketing material than that.
Adam imagines that he was hit with a weapon that was still in prototype, so innovative that even his attackers were not yet fully aware of what it could do.
But there isn't anything new about the idea of this sort of weapon.
Almost as soon as scientists discovered that they could create energy waves, there were inventors looking to weaponize them.
We came across an article from 1924 in the Scientific American that describes the promise of ray weapons as the true perennial of science.
Plans were shrouded in secrecy, leaving the magazine groping in the darkness for hard evidence that they existed.
But there were rumours that a French inventor had used a beam to paralyze taxicabs in Paris.
Marconi and Tesla, co-creators of the radio, were both said to be on the case.
Tesla claimed that his greatest invention yet would be a beam that would reduce an army to ashes and yet evade all detection.
Alongside these scientists, storytellers let their imaginations run wild.
Recently I came across a story that reminded me of retired CIA agent Suzanne Matthews and one of her strange experiences in Havana.
I was reading the Tintin book, The Calculus Affair, to my seven-year-old son.
In it, Captain Haddock, Tintin's borderline alcoholic companion, is relaxing with yet another glass of whiskey when it explodes in his hand.
In the comic, there's a satisfying explanation.
Outside, somewhere in the gloom, an ultrasonic weapon is being tested.
This book was written in the 1950s.
By then, the idea of an invisible ray gun was old hat in science fiction.
It seemed to hold unlimited promise.
And, as its special allure, it would be untraceable.
The ray gun was the white whale of weapons inventors.
Laws of physics apparently always keeping it just beyond reach.
But Adam was becoming convinced that someone had finally cracked it.
A deniable system.
There's no evidence left that it happened.
There's not a shell casing, there's not an imprint on the wall, there's not shattered glass, there's nothing.
It's just, it's like nothing was ever there.
Googling weapons technology was unfamiliar territory for Doug Smith at UPenn, but he couldn't help himself.
I really spent quite a bit of time looking up what could possibly account for this.
He was trying to figure out how his patients' experiences in Havana might be connected to their symptoms.
Smith believed that if this was a weapon, the sounds almost all the patients reported hearing must be a by-product,
like the sound of a gun firing, because he knew that regular sounds didn't cause the damage he was seeing.
Just audible sound can't hurt the brain.
It can hurt your ears if it's a high enough decibel, but it can't hurt your brain.
If this was an energy weapon, the question was, what kind of energy?
What other energy waves produce sounds?
I looked it up, googled it, and there was some studies of people with, you know, working on sonar or radar facilities
where they could hear kind of clicking or some kind of noise.
Radar operators first noticed this back in World War II, when radar was still newfangled technology,
using pulsed beams of microwaves to measure distance.
The microwaves created sound effects that occurred only inside the operator's head, like ringing in the ear.
If this was what was going on in Havana, it might explain the fact that the neighbours hadn't heard anything unusual.
And of course, sounds like this would not be picked up on those recordings the patients had made.
It might also account for the fact that the patients heard a wide range of sounds.
Some actually described kind of a low, metallic kind of grinding sound,
and others described kind of like a baffling sound, like if you're driving down the highway with the back window open.
So the sound wasn't consistent with all the patients.
Smith had found himself neck deep in a rabbit hole.
But figuring out what had put the patients in his clinic wasn't part of the professor's remit.
That wasn't really our expertise.
We didn't know what that was.
That wasn't part of our investigation.
The team were running the command and control centre for the medical response to Havana syndrome.
They were focused on rehab and getting people back to work.
As Smith understood it, this was top secret for government use only.
Then a few weeks into the project, Smith's contact in the government threw them a curveball.
He said, I think we should make this public, which is really quite surprising to me.
They wanted Smith's team to publish a paper in a scientific journal, which put them in a difficult position.
Ordinarily, they would only publish after a period of careful research under very different conditions.
This was never intended to be a research study.
This was just intended to evaluate and treat the patients.
Many on the UPenn team shared Smith's misgivings, but they rallied on behalf of the government.
The UPenn paper was posted online in February 2018.
It had been peer-reviewed and published in the prestigious Journal of American Medicine, JAMA.
And news outlets jumped on it as an official diagnosis of a novel illness.
We're discussing the mysterious illness known as Havana syndrome.
The Havana syndrome is a set of medical signs and symptoms reported by the United States.
It still surrounds those suffering from what's been called Havana syndrome.
The actual title of the paper was less catchy.
Neurological manifestations among U.S. government personnel reporting directional, audible, and sensory phenomena in Havana, Cuba.
This was not a declaration that directed energy had made the patient sick, but it implied a possible connection.
If the CIA had been worried about going out on a limb by withdrawing from Cuba,
the paper seemed to offer the credibility of scholarly research.
The U.S. government said it was a warning of an ongoing health risk.
Two weeks later, the State Department made the drawdown of the Havana embassy permanent,
designating Cuba an unaccompanied post, meaning no family, a measure usually reserved for war zones.
From the start, this paper was controversial.
Some of the criticism reflected the concerns Smith had about publishing.
He didn't have a control group and no baseline testing of, say, healthy diplomats from Havana,
all things he would usually have in a rigorous research study.
What's more, usually papers share their data.
But Smith says they couldn't do this for security reasons.
So readers struggled to discern for themselves if something really was out of the ordinary or not.
The information UPenn relied on to make their findings had to be taken on trust.
And many weren't prepared to do that.
They said it could be anything.
Some more mundane sickness.
A tropical virus.
A problem with pesticides.
That Cuban insect theory.
NPR gave it all a hearing.
Here's another theory.
The symptoms stem from a kind of collective stress response.
A few Americans heard an unfamiliar noise, maybe just cicadas, and thought it was making them sick.
Through the power of suggestion, dozens of others started feeling symptoms, too.
That's the conclusion of a panel of Cuban scientists.
But after his evaluation, Smith doesn't buy it.
There'd have to be almost like a grand conspiracy to go and research what concussion symptoms look like.
Come before a group of experts and convince each one that they had an issue.
And that's including going through some tests that you can't fake.
If the paper was meant to support these claims of attacks in Cuba, it ended up making matters worse for the patients.
They felt like they were being attacked again, almost.
All these wild claims about they're all making it up or that it was something even subconscious.
That bothered them.
You can't say nothing happened.
This is Mark Polymeropoulos, the senior CIA agent who reported being struck in a Moscow hotel room.
His symptoms weren't getting any better.
I had a headache for, I mean, a splitting migraine that never went away.
I was feeling the pressure on my head.
Occasional bouts of vertigo and occasional bouts of tinnitus, again, ringing in my ears.
He'd followed the fallout in the scientific community to the UPenn paper and thought the criticism was totally unfounded.
You know, how is this person at the top of their game in the espionage business at 30, 40 years old, and literally the next day they can barely function?
Ever since getting back to the U.S., he says he'd been trying to persuade his bosses to send him to UPenn where he could get treatment.
He says they continued to refuse.
So instead of a doctor, he found a lawyer.
I have been on this case now for a decade, long before the incident in Havana.
This is Mark Zaid, a prominent D.C. attorney, representing whistleblowers from the intelligence community.
For many years, until it was revoked during the current Trump administration, Zaid had security clearance privileges to help him investigate cases.
Through his work, Zaid has established a theory that connects Havana syndrome to a shadowy history of covert directed energy use.
In my view, what has been happening, although it has evolved, can trace its history literally back almost 60 years.
This theory began to take shape when he took on a client by the name of Mike Beck from the National Security Agency, an intelligence wing of the Department of Defense.
In 1996, when he was on a work trip with another colleague, they experienced, both of them experienced some sort of incident.
The two agents had been assigned to assess surveillance at a U.S. embassy in a hostile country.
While there, the agents got word from a source that they had ticked off the host government by snooping around a nearby building where they discovered a suspect device.
They braced for retaliation.
That night, Zaid's client believes, he and his partner were targeted in their hotel beds.
The following morning, he woke up feeling like a bowl of jelly.
A full decade later, both agents were diagnosed with Parkinson's disease while still in their 40s.
And he ended up having to retire because he was physically, medically unable to continue to do his required work week.
Zaid's client wanted his help joining the dots.
And we weren't able to get him workman's compensation because we, first, we were struggling with being able to demonstrate that, in fact, he was attacked.
Zaid wasn't officially told which country this incident took place in, though he has a pretty good idea.
I've not been cleared to know, actually, that it was in Russia, but it makes sense.
And that opened up a whole new avenue for Zaid's legal investigation.
As he went deeper, it felt to Zaid like he was uncovering a history that had been deliberately buried.
One day, a friend of his came by with a box of slides.
Kodachrome slides.
You know, the old-fashioned slides, which probably most of the people listening to the podcast don't even know what the hell they are.
This is like the kind of holiday snaps thing where you stick them in.
Yeah, you put it in the machine, and it's a square, and it goes around on a carousel, and, you know, these are slides.
The slides are photographs someone's taken of a series of retro illustrations.
They appear to be diagrams of how energy rays could be beamed from one building to another.
One slide, titled infrared, shows a solid line.
The other, a kind of pulsed beam, is titled microwave.
Both rays are being directed at a building marked Target.
And these slides are from sometime around 1970.
There's no way to prove their provenance, that is, who produced them, why, when, where, and exactly what they're intended to show.
You know, is it for surveillance? Is it weaponized? There's no indication at all.
They even look kind of phony, like they could have been made for an art project.
But Zaid says the slides belonged to his friend's father, who used to work at the CIA in the 1970s, when he says these slides were made.
And at that very moment in history, the CIA was trying to get a handle on an evolving situation in Moscow.
The Soviets were bathing the U.S. embassy in microwaves.
It was called the Moscow signal.
And it seemed to Zaid that these old slides were an artifact from a race between Russia and the U.S.
You've heard of the space race, the nuclear arms race.
Well, there was also the ZapGap.
The American fear that in the race for a microwave weapon, the Soviets were a step ahead.
Whenever you get into microwaves, you get into the unknown.
The Soviets and now the Russians, I have this feeling that they've always been way ahead of us.
So they're doing things that we don't quite understand.
This is former diplomat Jim Shoemaker, who was posted to the Moscow embassy back then.
We got in touch with Shoemaker after reading an article he wrote called Before Havana Syndrome, There Was Moscow Signal.
The things that are similar about Havana Syndrome and Moscow Signal is the possibility that there's some kind of directed energy or microwave connection.
And the other similarity is how initially the U.S. government simply tried to ignore the entire issue.
Shoemaker told us a story that starts in 1945.
Soviet schoolchildren gave a carving of the Great Seal of the United States to the U.S. ambassador.
Very touching.
It hung in the ambassador's Moscow residential office until 1951,
when the State Department discovered that information from private meetings in that room was getting out.
It turned out that the gift from the Soviet schoolchildren was fitted with a bug.
It looked like a kind of a clock with one hand inside the seal itself.
A technician at the residence slept with it under his pillow at night,
fearful the Soviets would steal the bug back before he could unlock its secrets.
There were no wires, no batteries.
The Soviets seemed able to switch this on and off remotely.
The Americans gave it a nickname.
The thing.
People didn't know quite what to make of it.
That's funny because that's what they ended up calling Havana Syndrome before they came up with Havana Syndrome.
No, I didn't know that.
The thing was invented by Leon Theremin,
here playing his most famous invention,
the first ever electronic musical instrument, called the theremin.
Played by waving your hands through a radio signal travelling between two brass orbs,
it became a staple in sci-fi shows.
But to his 1930s audiences, it must have seemed like magic,
like plucking music out of thin air.
Theremin was a physics professor and genius at creating eavesdropping systems.
Initially working from a secret laboratory in the Gulag where he'd been imprisoned,
he used infrared and then microwaves to trigger his eavesdropping devices,
making the thing almost impossible to detect.
It had to be operating at the time that you were trying to detect it.
When it was hit by a certain frequency, it would vibrate.
An American ambassador would later produce the seal and bug at a meeting of the UN
to demonstrate the depths of Soviet espionage.
The Soviets are really, really good at listening in on conversations.
Meanwhile, across town in Moscow, another American technician
discovered a low-strength microwave signal was being beamed at the newly built U.S. embassy.
From across the street, from the roof of an apartment building there.
By the early 60s, the Americans had established the embassy was being bombarded
with low-level microwaves, more or less around the clock.
But why?
Was it more surveillance?
Were the Soviets activating bugs?
One theory was that bouncing microwaves off the windows
could amplify conversations inside.
The signal strength was below American safety standards,
so they didn't think it was being used as a weapon.
But they couldn't be sure.
So in 1965, back in the U.S.,
they began to commission secret studies with codenames like
Project Pandora, Bazaar, and Big Boy.
They blasted primates with their own version of the Moscow signal.
The head of that trial was excited by the possible military applications of microwaves.
But his experiments were dogged by measuring errors and bad practice,
poorly designed restraints, injured and even killed some of the animals.
The microwaves seemed to have little effect, and the trials were scrapped.
But the man in charge of them reflected,
My feeling is we probably should have continued longer with the research in that area,
and not necessarily concluded it that early.
There were a lot of unknowns, and I don't think they were ever really put to bed.
If that research had come about in order to find out whether the Moscow signal was harmful,
well, the U.S. still didn't know.
They wanted answers.
It's just that they were still trying to keep it all a secret.
You know, they had been keeping a lid on it for various policy reasons of their own.
They managed to obtain some blood samples in 1965
by telling staff it was research into the viruses that were a feature of Soviet winters.
They learned little from those samples,
but they ignored advice to install conspicuous lining on the windows.
Still, word began to spread,
and by 1970, the situation in Moscow had become an open secret in Washington.
Henry Kissinger confronted his Soviet counterpart about it,
telling him that too many people knew about the microwave signal,
and the U.S. government would catch hell unless they could show they were doing something about it.
The Russian replied,
What signal?
At this point, the State Department took an interesting precaution.
Just like with Havana syndrome, they prepared a briefing note,
ready should any reporter come asking awkward questions about the Moscow signal.
No one did, and the briefing note was quietly filed away.
They were finally found out when Ambassador Walter Stessel Jr. turned up at the end of 1974
and learned of the situation.
The distinguished diplomat, now heading up the embassy in Moscow,
was appalled that this had all been kept a secret.
Ambassador Stessel, you know, he threatened to quit,
and so they allowed him to brief the staff,
and that's when it all blew up, in early 1976.
That year, the Soviets did finally admit that they were indeed responsible for the microwave signal,
but they claimed they were using it as a countermeasure to jam American spy signals,
an explanation the Americans accepted.
With the story public, health concerns began to emerge.
A State Department doctor reported that several members of the embassy staff
displayed symptoms, including severe headaches, inability to concentrate, and fatigue.
But that same doctor put the symptoms down to the psychic stress
connected to the perceived threats of working at the embassy.
It was in the middle of all this, with no questions answered,
that Shoemaker arrived in Moscow, appointed as ambassador's aide.
The thing is, it was during the Cold War, when, I guess, the sides were clearer,
and when, I guess, our moral certainty was clearer.
He knew all about the microwave story.
He'd read about it in the papers.
But he and his colleagues shrugged it off.
You know, it's like you were a soldier in a war zone.
You know, if the enemy hits you with a mortar or a grenade,
you're not going to complain to the enemy about it or file a suit against him.
You're just going to shoot back.
But shortly after leaving Moscow, Shoemaker regretted his cavalier attitude.
Well, I honestly didn't expect to live this long.
But, you know, I'm sort of surrounded now by a platoon of doctors.
During his end of tour physical in 1979, something showed up in his blood tests.
Well, they told me I had a very high white count, just sort of out of the blue.
I didn't know this at the time, but apparently a lot of people at Moscow were coming back from their tour with a very high white count.
The State Department had established this right after Moscow's signal became public.
They took blood tests, which showed that many workers had high white blood cell counts, but established little else.
And their study was abandoned within the year, before Shoemaker even arrived in Moscow.
Shoemaker says that an unusual number of Moscow embassy staff from that time ended up getting rare forms of cancer.
There was a group of us, kind of a Moscow reunion group.
We would meet once a year.
And there you got to see how everyone was doing.
Ambassador Stessel, having stood up for his staff's right to know, also contracted leukemia and died from it in 1986.
No study has ever established a link between these illnesses and what happened in Moscow.
But Shoemaker says it felt like the government could have done more to answer their questions.
Without a long-term study, it was left to him and his colleagues to put it together themselves.
So all you can point to is like anecdotal evidence.
I have to face the reality that I went to Moscow in perfect health and came back with a high white cell count.
The whole thing is just a bottomless pit.
I mean, the deeper you go, you know, it's like a black hole.
You never get to the bottom of it.
You could read the Moscow Signal as a cautionary tale about government mismanagement of a health scare.
But to that lawyer Mark Zaid, the Moscow Signal demonstrated Soviet steps towards a microwave weapon.
For years, a lot of this stayed underground.
In 2014, he received something interesting.
He spent months trying to push the U.S. government for answers on his client who got targeted in, he suspects, Russia.
Finally, he got something back.
So NSA gave me a short memo, unclassified, dated October 16, 2014, that says,
The NSA confirms that there is intelligence information from 2012 associating the hostile country to which Mr. Beck traveled in the late 90s with a high powered microwave system weapon that may have the ability to weaken, intimidate or kill an enemy over time and without leaving evidence.
There's a surprising amount of detail about this weapon the NSA had heard tell of.
The 2012 intelligence information indicated that this weapon is designed to bathe the target's living quarters in microwaves, causing numerous physical effects, including a damaged nervous system.
But it went on to say there was no evidence that such a weapon, if indeed it did exist, was used on Zaid's client.
So it's a very legalistic, written memo that, on the surface, says a lot.
Going down deep says absolutely nothing.
It wasn't the proof Zaid needed for his NSA client.
But when Havana syndrome appeared, he felt sure the Russians were up to their old tricks.
In September 2018, the microwaves theory went public, and the media marveled at the ingenuity of the idea.
Correspondent Patrick Hartman is in Havana with details on this new twist in the investigation.
In a way, you read about these weapons and these weapons programs that did exist, and it's kind of the perfect weapon because it leaves no trace.
Doctors as scientists involved in the explanation are considering microwave attacks to be the main suspect.
In the media, Havana syndrome was beginning to sound like science fiction again.
Even Doug Smith from UPenn weighed in.
Dr. Douglas Smith of the University of Pennsylvania says microwaves are one of several possible explanations for the brain network disorder.
But he and his team are now conducting advanced MRI tests to study these employees' brains and see what's wrong.
UPenn's neuroimaging expert was Ragini Verma.
Dr. Ragini Verma, I guess.
So I have a PhD in math and computer science, so I'm a quintessential Indian kid in that way.
Lots of math and computer science.
UPenn had already performed brain scans on the patients.
Regular MRIs, the type that are used in hospitals everywhere.
Those didn't flag anything.
But Smith wanted to probe further.
And Dr. Smith said, can you do an analysis just to make sure that we aren't missing something?
He brought in Verma to use cutting-edge neuroimaging techniques.
If they ever wanted to publish, they were going out on a limb.
This wasn't just new.
It was usually used to look for patterns among large groups of patients.
Verma was looking at just 20 or so.
But they figured it was worth a shot.
So we put in the groups and controls and we did the analysis.
And I must say that I was blown away, that there was a very significant group difference.
Verma says she found a pattern, not a definite sign of injury as such, but changes, subtle ones, in the cerebellum, the part of the brain that controls balance and memory.
She took her findings to a colleague who had worked closely with the patients.
So then I reached out to Dr. Swanson and I said, we are seeing differences in this part of the brain.
It's called the cerebellum.
And I said, is this relevant?
And he basically walked across to have a chat saying, oh my God, this is so relevant.
This is where all their problems are.
Verma says she noticed that in that part of the brain, the patients had lost a tiny amount of fluid.
She told me about a minor eureka moment she had one day in the UPenn clinic kitchen.
She was looking at a container of noodles someone had left in the microwave for too long, leaving them completely dried out.
Maybe microwaves could have caused the loss of fluid in the brain scans that Verma had seen.
At a high enough power, microwaves would cause injury.
But as one expert put it, like a microwave oven, they'd fry the outside of your skull on the way in.
So not exactly untraceable.
But could a pulsed beam, short, rapid pulses of high-powered microwaves damage the brain without turning you into popcorn?
It pointed back to that research that Doug Smith at UPenn had come across months earlier about those radar operators in World War II.
Radar uses pulsed microwaves.
And those operators reported clicking and whirring noises inside their heads.
Could this explain those funny noises that people perceived in Havana?
Well, in the 1960s, a biologist studied the noises that pulsed microwaves seemed to trigger.
His name is Alan Frey.
He's now 90 and living in Virginia.
So I knocked on his door.
Nowadays, most people call it the Frey effect.
Frey himself used to call it a sonic delusion.
This is how it works.
Soft tissues in the head absorb the microwave pulses.
That launches a wave of pressure that travels to the inner ear, where it activates the cochlea.
It's the cochlea that absorbs sound waves.
That's how we hear.
But these waves come at it from the other direction, from inside the head.
Like bubbles popping on top of a fizzy drink.
Deaf people can hear them too.
Frey and I talked a little in his front garden about how any of this might relate to Havana syndrome.
I wanted to chew the fat with him.
The effects Frey had documented were harmless.
His experiments had all been conducted at levels way below the safety limit for microwave exposure.
What would happen if you used stronger pulses?
For obvious reasons, a study like that would be problematic.
If anyone's done it, certainly they haven't released the findings.
But what did he think?
At first reluctant, he agreed to an interview.
But when I called him the following morning, Frey told me a contact of his in the US government advised him not to speak on tape.
He said it was all just too sensitive.
Frey did say this, though.
When I asked him, could the Frey effect have been weaponised and used against those people in Havana, Frey said it was a theory looking for a reality to attach itself to.
It was frustrating.
We'd come to the door of the man whose work the whole microwave theory rests on.
And all he could offer was a shrug.
On the hunt for the untraceable weapon, people told us there is a line to connect this Cold War history to Havana syndrome.
But like those 1920s journalists from the Scientific American, we're left groping in the darkness for evidence.
There was something quaint about this history, from the age of reds under the bed.
Arthur Miller said fear doesn't travel well.
What terrifies one generation is likely to bring only a puzzled smile to the next.
Next time on Havana Helmet Club.
We assumed after the Soviet Union ceased to exist, you know, you had the end of history and so forth, that we never would have to face existential threats.
We went to sleep for a while and we didn't pay attention financially to what we needed to provide our military with.
And now the bill is due.
Had I been met in fact in a halfway timely manner, especially my kids' injuries, but my injuries as well and my wife's, would not have been nearly as bad as they are.
How would that make you feel?
It's outrageous.
Outrageous.
Now it's an attack on the home front.
Now it's, wow, everyone is vulnerable.
If folks are easily targetable, what's to stop whoever this is from doing it to the President of the United States?
I don't think anything accidental happens to American diplomats in hostile countries.
From BBC Radio 4, this is Havana Helmet Club.
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Havana Helmet Club is written and presented by Sam Bungee and Jennifer Ford and edited by Guy Crossman.
Our story editor is Mike Olive and our producer is Larry Ryan.
Original music by Tom Pintons.
Sound design by Meryn Royards.
Additional sound design and mix by Peregrine Andrews.
Commissioning editor for the BBC is Dylan Haskins.
Assistant commissioners are Sarah Green and Natasha Johansson.
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