In the last 10 months, six senior Russian diplomats and one former intelligence officer have died while serving around the world. The most recent was Russia's ambassador to Sudan, who died Wednesday. Police say he suffered a heart attack while swimming at his Khartoum home and that foul play is not suspected.

But as CNN notes, there are indications of a pattern here.

The story begins on U.S. Election Day, last Nov. 8, 2016, with the New York consul death of Sergei Krivov, a security supervisor (responsible for preventing any U.S. efforts to spy on the consulate). Russian officials first claimed that Krivov fell off a roof, but then said he died of a heart attack. The New York Medical Examiner found that he had actually died of internal bleeding and had been in ill-health. Note, however, that when Russians speak about falling out of windows or off roofs, it is their way of attempting dark humor.

Regardless, just a month later, a senior Russian diplomat, Petr Polshikov, was found dead in his Moscow home. Although he had been shot and had a pillow over his face, Russia immediately described Polshikov's death as a suicide. Six days later, a retired senior officer of Russia's FSB domestic intelligence service was found dead in his Moscow car.

Next, in early January, the head of consular affairs for the Russian Embassy in Greece was found dead in his Athens home. Also in January, Russia's Ambassador to India, Alexander Kadakin, died after what was described as a short illness.

Finally, there's Vitaly Churkin, Russia's former UN ambassador, who died in his New York office in February. Once again, a heart attack was blamed.

So what's going on here?

Perhaps nothing. Diplomats are humans just like you and me, neither immune to heart attacks or to any other disease. And partly due to their drinking habits, Russian men have higher than usual rates of heart disease.

Still, that so many senior diplomats have died in such a short period of time is interesting. It invites us into what CIA spy hunter, James Angleton, referred to as the wilderness of mirrors. The most obvious conspiracy theory that comes out of the mirrors is that at least some of the deaths were caused by assassins.

And if we assume that, then we must also assume that Russian intelligence is responsible for killing its own people.

The primary threat to Russian diplomats is that posed by Russian separatists and Islamic extremists. However, those groups would struggle to assassinate on such a global scale as this, and with such plausible deniability. By deniability, I mean causing heart attacks or illnesses in a way that makes them appear natural. While it is possible to use such means of assassination (Israel's Mossad is exceptionally skilled at doing so), it also takes a lot of planning, patience, and competence. Few intelligence services have that mix of abilities.

Russia, however, is one of them: it loves using poisons to kill targets in both overt (Alexander Litvinenko) and covert ways ( don't run in Surrey, England).

But why would the Russians kill their own officials?

Again, only two possibilities arise. The first possibility is if the officials were political rivals or opponents to Vladimir Putin, or had offended him. There is no evidence to suggest that is the case with any of the dead here, so that leaves one other option: Russia's belief that the diplomats were providing intelligence to a foreign power.

In that context, the locations in which some of the deceased perished is interesting. For one, African nations such as Sudan are used by many intelligence services to give their new officers the skills to recruit sources. Athens and New Delhi are also two top espionage capitals, serving as hub destinations for many trade and political delegations from across the world.

And that matters because most intelligence service recruitment of foreign officials does not occur in the nation where that official is actually from. Put simply, if country A has recruited a government official from country B, it is very likely that the recruitment first occurred in country A or country C, rather than in country B. In this regard, foreign capitals like Athens and New Delhi make an attractive proposition because Greece and India lack the counter-intelligence presence and public attention of capitals such as Beijing, Moscow, or Washington, D.C.

I recognize we're descending into the wilderness of mirrors here, but stay with me.

Because if we assume that some of the dead diplomats were spying for a foreign nation and were killed by their government for it, we must also ask how they were identified.

From my perspective, only one possibility stands out: a traitor in country A told country B that country A was successfully running a country B source. The underlying issue here is the timeline. After all, without inside information, it would be almost impossible for the Russians to identify so many double agents in so many locales in such a short period of time. Yet considering the rank of some of these officials, it also means country A's traitor would have to be very high-ranking. That's because intelligence services take extreme efforts to protect the identity of those who are spying for them. Those sources are the crown jewels of intelligence, responsible for long-term contributions to intelligence products. Only the very highest ranks get to know a source's true identity.

Ultimately, I believe most of these individuals simply died of natural causes. Still, three stand out as highly suspicious: First, because of Russia's changing story on causation, the death of Krivov in New York. Second, because they died abruptly in suspicious circumstances in Moscow, Polshikov and the former FSB intelligence officer.

Oh, and one final thing to ponder. If Krivov and Kadakin were indeed in ill-health prior to their deaths, why weren't they ordered back to Moscow for treatment?

Or perhaps they were and said no?

Who knows.

Whatever, these deaths make for a good spy story!