It's the stuff of a diplomatic thriller, but it's real.
Washington is threatening to shutter the US embassy in Havana because diplomats are keeling over, suffering strange symptoms in what Washington believes is a clandestine attack on its recently re-opened mission in the Cuban capital.
More than 20 diplomats and/or their spouses have been repatriated or are being treated in Havana for what their staff association describes as "mild traumatic brain injury and permanent hearing loss, with ... loss of balance, severe headaches, cognitive disruption, and brain swelling."
Describing the symptoms as akin to a concussion, government officials say that the hearing loss for some of the victims could be permanent.
Investigators - American and Cuban - are baffled, as much by the illnesses which started soon after the American diplomatic return to Havana late in 2016; as by the sophisticated weaponry that might have been deployed against them.
Secretary of State Rex Tillerson calls it a 'health attack.' The staff association used the term 'sonic harassment attacks.'
In background briefings, US officials have described an 'acoustic' attack, citing a device they claim works beyond the range of audible sound that was used on the diplomats, not at the embassy building, but in their Cuban-provided and maintained homes - affecting adults, but not children.
Some of the victims described to Associated Press feelings of walking into what seemed like powerful beams of sound in certain rooms or even only parts of rooms in their homes.
But Boston-based acoustic expert Joseph Pompei told Fairfax Media: "Sound waves in air simply do not penetrate the body in any meaningful way; nearly 100 per cent of the energy is reflected."
The victim list doesn't make sense. While any of dozens of countries or terrorist groups have beefs with Washington, a single Canadian diplomat reportedly is among the victims.
Ottawa has historically enjoyed cordial relations with the Castro regime but it's not inconceivable that a Canadian was mistaken for an American.
The Cuban government is a key suspect, because the attacks are happening in that country. The Trump administration is applying pressure, but treading gingerly.
It expelled two Cuban diplomats in May, but kept the expulsions under wraps till August.
At the same time, Washington is not discounting the apparent sincerity of Havana's denials of complicity - exemplified best by its rare willingness to allow FBI agents to travel to Cuba to join the investigation.
The timing doesn't make obvious sense.
Harassment of US diplomats in Cuba - break-ins, to homes and cars - was considered to be government sanctioned before the Obama d??tente, but Havana benefits significantly from the easing of hostilities.
Which is why investigators have not ruled out a campaign by some other government.
But the suspects also include a rogue Cuban element operating without Havana's authority - because, they say, the tenacity of Havana's domestic surveillance apparatus would make it very difficult for non-Cuban agents to operate in secret on its turf.
One theory is that the attacks are a 'payback' mission for American activity elsewhere, by disrupting relations that thawed significantly under the Obama administration - but which have chilled somewhat under Donald Trump, who describes the thaw as a "terrible and misguided deal."
Trump criticised the regime in his Tuesday speech at the UN General Assembly in New York - and the mystery attacks on the embassy present a golden opportunity for closure - if he wants to be more bite than bark.
Republicans in Congress are agitating too - five of them wrote to Tillerson last week demanding the expulsion of all Cuban diplomats in the US if Havana does not resolve the issue.
Another line of American speculation is that the injuries were caused by some kind of surveillance operation gone wrong.
When the diplomatic expulsions became news in August, the Cuban Foreign Ministry denounced them as unjustified and unfounded,"; saying in a statement: "The Ministry emphatically emphasizes that Cuba has never allowed ... Cuban territory to be used for any action against accredited diplomatic officials or their families, without exception."
State Department spokesperson Heather Nauert told reporters: "We're not assigning responsibility at this point. We don't know who the perpetrator was of these incidents.
It's an aggressive investigation that and we'll continue doing this until we find out who or what is responsible for this."
Tillerson revealed that closing the embassy was 'under evaluation" during an interview on CBS's Face the Nation on Sunday, saying: "It's a very serious issue with respect to the harm that certain individuals have suffered. We've brought some of those people home. It's under review."
But on the limited information available, experts like Pompei, whose expertise is physical acoustics, how sound travels, and psychoacoustics, how it is perceived and processed by the human brain, are sceptical about the theorising around a sonic attack.
"I am quite confident that this cannot be the cause," he said in an email exchange.
A "sonic attack" doesn't exist, at least not in the conventional understanding of those terms. I have never heard of one, outside of using loud noises to irritate or annoy people. Such 'attacks' are obvious and not very interesting, and typically just involve big loudspeakers."
Pompei said that while it was conceivable that high levels of high frequency, near-ultrasonic signals might be bothersome, like any loud sound, there was little evidence they could cause broadband hearing loss, and no evidence whatsoever that they could cause the other physiological symptoms experienced by the diplomats in Havana.
Besides, the equipment needed would be so big and obvious that it could not be used in a secret attack.
"It's an attractive speculation because it's seen as exotic. People don't understand sound very well, so they don't know how impractical it is, or how limited it is as an attack vector," he said.
"But any expert in the field will agree that it's a very unlikely explanation for what the diplomats have been experiencing."
However, he did not exclude the possibility of a powerful radio-frequency device - "RF transmitters have been known to stimulate perceived sounds, can penetrate tissue and cause physiological problems, and can penetrate walls, so a device can be hidden.
"This seems most likely to me, but it is still pure speculation." In which case, the attackers are breaking new ground, because Pompei goes on: "RF effects on hearing have been studied, of course, but I've never heard of it being weaponised."
And he's hesitant to keep RF in the equation because it too would require cumbersome equipment.
Could it be a surveillance operation gone wrong, as speculated by the investigators?
"It's conceivable that, if it were RF, it could be a side effect of a clumsy or malfunctioning eavesdropping device, but I would not expect any competent government agency to make such an egregious mistake."
And asked to lend credence to Fairfax's diplomatic thriller scenario, Pompei becomes a killjoy.
"So far, there is no hard evidence that there is any political/diplomatic thriller here whatsoever," he spoils.
"Hearing loss, brain swelling, and similar symptoms are consistent with inadvertent exposure to various chemicals, and the exposure, that could have happened accidentally. It could have been paint, solvent, aerosol, or other usually mundane substance.
"It could conceivably have been mold spores, or another infectious agent."
And after that downer, Pompei offers just a slender thread of credibility, predicated on a cautious 'if:'
"If an attack is assumed, radio frequency is a likely candidate."
