They were amateurs with gum wrappers and peanut butter. And they nearly sold US military secrets.

"This is not a hoax."

The claim was among the most tantalizing elements of a proposal allegedly proffered by a Navy engineer looking to cash in on the sale of secret design data for sophisticated nuclear-powered submarines in the U.S. fleet.

In virtually every respect, the offer was extraordinary as was the intelligence risk to the U.S.

But the operation may never have been thwarted, resulting in last week’s arrest of Jonathan Toebbe and his wife, Diana, if the foreign country that Toebbe approached had chosen to do something other than turn over the evidence to the U.S. last December.

Within six days of receiving the alleged solicitation, an undercover FBI agent established contact on a prearranged encrypted channel with the engineer, ultimately leading to clandestine drop sites of digital memory cards concealed in a peanut butter sandwich and gum wrappers.

The Annapolis, Maryland, couple, charged with violating the Atomic Energy Act, face the prospect of life prison terms if convicted.

What if 'Country 1' hadn't alerted the FBI?

Yet as the Toebbes await detention hearings Wednesday in a West Virginia federal court, the unusual case of alleged espionage raises new questions about the security of sensitive U.S. data, while highlighting a decidedly amateurish spy-craft effort to find a willing foreign partner.

The dramatic role played by that country, which court documents refer to only as "Country 1," appeared to provide U.S. authorities with the necessary break to avert a damaging loss.

"By all accounts, the (shared) information was critical," said Philip Mudd, a former CIA official who also served as deputy director of the FBI's National Security Branch. "Unless there was an opportunity to see the information downloading to a thumb drive or something, I'm not sure you get such a jump (on the investigation)."

David Weinstein, a former federal prosecutor in Florida, said such cases rarely land in the laps of federal investigators, let alone in the same way, suggesting that the solicitation could have avoided U.S. detection had the country not turned it over.

"I don't know, maybe 50-50 they find out eventually," Weinstein said. "This was more an example of fiction becoming reality."

Indeed, Mudd said the engineer's alleged proposal and subsequent communications with an undercover FBI agent resembled "more Peter Sellers than Aldrich Ames," in a comparison between the bumbling Pink Panther character of movie fame to the deadly real former CIA counterintelligence officer convicted of selling secrets to Russia.

"The first approach is you send a letter to somebody you don't know and hope to strike a deal? Why would anybody do that?" Mudd said.

The awkward dance of 'Bob' and 'Alice'

The apparent awkwardness is a theme that runs through much of the government's 23-page affidavit, detailing contacts between the agent and the engineer who assumed the respective pseudonyms of "Bob" and "Alice."

“I apologize for this poor translation into your language," Alice wrote in the initial solicitation. "Please forward this letter to your military intelligence agency. I believe this information will be of great value to your nation. This is not a hoax.”

The message, along with printouts, operations manuals, and performance reports, was contained in a brown paper envelope carrying a return address in Pittsburgh, Pennsylvania. Once the package was delivered to the FBI, a monthslong correspondence ensued that exposed a mix of fear, self-deprecation and determination to capitalize on access to sensitive information.

“I am uncomfortable with this arrangement," the suspect writes in a March 5 note, arguing against a live meeting with the person he believed to be his handler. "Face-to-face meetings are very risky for me, as I am sure you understand.

"I propose exchanging gifts electronically, for mutual safety," the message goes on:

When the discussion moved to planning for the actual exchange of information through a series of "dead drops," the rising stakes seemed to conjure even more anxiety.

"I am concerned that using a dead drop location your friend prepares makes me very vulnerable," Alice tells the agent. "If other interested parties are observing the location, I will be unable to detect them. l am not a professional, and do not have a team supporting me. ... For now, I must consider the possibility that you are not the person I hope you are."

The following month, according to court documents, Alice continues to push back on a plan for a handler-arranged drop site and asks for a sign as insurance that he is dealing with an honest broker.

“I am sorry to be so stubborn and untrusting, but I can not agree to go to a location of your choosing," Alice writes in a April 9 message. "I must consider the possibility that l am communicating with an adversary who has intercepted my first message and is attempting to expose me. Would not such an adversary wish me to go to a place of his choosing, knowing that an amateur will be unlikely to detect his surveillance?"

The contact prompts a compromise and some flattery in an apparent attempt to keep the lines of communication flowing.

"You do not need to apologize," Bob writes two weeks later. "We appreciate you being careful. That is much better than someone reckless. Your thoughtful plans indicate you are not amateur. This relationship requires mutual comfort."

For good measure, Bob discusses a plan for the display of a signal during the Memorial Day weekend at a location "associated with Country 1" to provide more assurance for his new partner.

"We hope this plan will continue to build necessary trust and comfort of our identity," Bob writes in a April 23 message.

Unlikely operatives

Nothing immediately stands out about the split-level home in the Hillsmere neighborhood near Annapolis, much like the longtime government engineer and local teacher who have lived there.

Since 2012, according to court documents, Jonathan Toebbe had worked as a Navy nuclear engineer whose assignments included stints at the Reactor Engineering Division, which deals with such matters as reactor plant noise and vibration technology.

Toebbe also had been assigned to a government laboratory near Pittsburgh involved in the design and development of nuclear power for the Navy.

Diana Toebbe, meanwhile, had worked as a faculty member and humanities instructor at the Annapolis-area Key School since 2012 until her arrest last week.

Matthew Nespole, the campus' head of school, said Toebbe has since been suspended.

"Key School is shocked and appalled to learn of the charges filed against faculty member Diana Toebbe and Jonathan Toebbe," Nespole said. "Key School had no prior knowledge of their alleged criminal activities, nor is the School connected to the investigation in any way."

The couple's lawyers declined to comment.

As part of the investigation, prosecutors have claimed that Jonathan Toebbe, at both of his Naval assignments, had access to the materials subsequently delivered last year to "Country 1" and left at drop sites this summer in Jefferson County, West Virginia, where Diana Toebbe allegedly served as a lookout, and a location in eastern Virginia.

Mark Zaid, a Washington, D.C., lawyer who specializes in national security issues, said that while the correspondence contained in the court documents appear to show someone "out of his depth in how to handle these things," the case also underscores a challenge for the government in monitoring sensitive information in the hands of people who have authorized access to it.

"What fascinates me the most is what prompted the person to contact the foreign country, and what led the foreign country to contact the U.S.?" Zaid said.

The questions are among many left unanswered by the court documents.

Not an ordinary peanut butter sandwich

Money, however, appears central to the suspect's planning.

According to court documents, Alice provided detailed instructions for how exchanges of thousands of dollars in cryptocurrency should be managed, while the undercover FBI agent worked in early June to transfer $10,000 as "a sign of good faith and trust."

After receiving the payment June 17, the relationship was poised to cross another threshold – data drops at predetermined locations with Alice writing that he was "eagerly waiting for your instructions.”

On the morning of June 26, with his wife allegedly serving as a lookout, the engineer proceeded to a drop location in West Virginia where the FBI was watching.

"Based on my experience and training, it appeared that Diana Toebbe assisted Jonathan Toebbe during the dead drop operation," according to the FBI affidavit, adding that the wife allegedly signaled to her husband to "proceed on a trail" after he completed the drop.

Later that day, the FBI recovered an unusual package left behind.

"The (memory) card was wrapped in plastic and placed between two slices of bread on a half of a peanut butter sandwich," the FBI affidavit said. "The half sandwich was housed inside of a plastic bag."

This article originally appeared on USA TODAY: Navy nuclear engineer, Jonathan Toebbe, could face life for espionage