Welcome to Ukraine-gate, the latest allegation of corruption in President Donald Trump’s administration and a uniquely confusing chapter in the commander in chief’s tense relationship with the men and women of the US intelligence community.

The burgeoning scandal swept into public view 10 days ago with an odd, unexpected Friday night letter from House Intelligence Committee chair Adam Schiff. Addressed to the acting director of national intelligence, Joseph Maguire, the letter discusses an apparent whistle-blower complaint, filed to the intelligence community’s inspector general last month, of what’s known as “urgent concern”—specific legal language that normally triggers congressional involvement. Except the House committee had yet to receive any complaint, and so Schiff’s letter was accompanied by a subpoena for the information Maguire was refusing to share.

“Even though the disclosure was made by an individual within the intelligence community through lawful channels, you have improperly withheld that disclosure on the basis that, in your view, the complaint concerns conduct by someone outside of the intelligence community and because the complaint involves confidential and potentially privileged communications,” Schiff wrote.

Since then, reporting by The New York Times, The Washington Post, and The Wall Street Journal has filled in some of the details of that whistle-blower complaint, suggesting that it centers at least in part on communications between President Trump and Ukrainian president Volodymyr Zelensky. The revelations have brought renewed scrutiny to relations between the two countries, particularly Trump’s decision to withhold military aid to Ukraine until earlier this month, as well as a long-running effort by the president’s personal lawyer, Rudy Giuliani, to encourage investigations into Democratic candidate Joe Biden and his son Hunter, who had connections to an energy company there. According to the WSJ, on a July 25 phone call with Zelensky, Trump urged the Ukrainian president to investigate Hunter Biden eight times.

Trump confirmed to reporters Sunday that he did bring up the Bidens on that call, but insisted there was “no quid pro quo.” It’s also worth noting that allegations of impropriety in Ukraine by either Biden have been soundly dismissed by those who have followed the matter most closely; Ukraine’s top prosecutor told Bloomberg in May that he had no evidence of wrongdoing.

If you’ve struggled to keep up with these developments, you’re hardly alone.

At the end of the day, though, the scandal boils down to this: The US president is alleged to have used the weight of his office to pressure a foreign nation into investigating a political opponent. If true, such behavior would clearly represent an abuse of power, precisely among the “high crimes and misdemeanors” that the nation's founders intended to be an impeachable offense.

“I have been very reluctant to go down the path of impeachment,” Schiff, whose outrage with the administration has been remarkably restrained, told CNN’s Jake Tapper over the weekend. “But if the president is essentially withholding military aid at the same time that he is trying to browbeat a foreign leader into doing something illicit—that is, providing dirt on his opponent during a presidential campaign—then that may be the only remedy that is co-equal to the evil that conduct represents.”

Maguire is set to testify before Congress later this week. So far he has refused to hand over the whistle-blower information to Congress, even as the law appears to leave him little room to stonewall Schiff and his committee. Trump, in tried and true fashion, has dismissed the whole thing as “Ukraine witch hunt.” On Monday, he publicly wondered about the whistle-blower, "Is he on our Country’s side. Where does he come from."

The Ukraine scandal, as it unfurls, brings together two central and ongoing problems of the Trump administration: foreign interference in US elections, and the White House’s tense relationship with its own intelligence community.

As acting DNI, Maguire oversees a $60 billion intelligence apparatus made up of tens of thousands of nonpartisan, career civil servants spread across 17 different agencies. They show up to work each day to keep the country safe and ensure the president has access to the best information that technology and human sources can provide. They are also people to whom Trump often refers, insultingly and inaccurately, as the “deep state”—an obscure phrase that Trump has so popularized that Merriam-Webster added it this month to the dictionary, defining it as “an alleged secret governmental network operating extralegally.”