An abrupt resignation, like Michael Flynn’s announcement Monday night that he would leave his post as national security adviser, is a beginning masquerading as a conclusion. His departure resolves one straightforward question—Can Flynn survive, having admittedly misled the vice president and the American people?—but raises a host of more important, and more complex, questions. In most cases, it’s far too early to guess what the answers might be, but here’s a rundown of some of the most pressing mysteries Tuesday.

Who replaces Flynn?

On a mechanical level, the question of who becomes the president’s top aide on security now is an important, urgent one. Not only has Flynn resigned, but his deputy, K.T. McFarland, is expected to leave the White House too, The New York Times reported. (McFarland, whose main credential was her frequent media commentary, would have been a surprising pick to be elevated.) Retired Lieutenant General Keith Kellogg, who had been serving as chief of staff of the National Security Council, has been named as Flynn’s interim replacement, and is reportedly a candidate for the permanent job. Other candidates include David Petraeus, the retired general and former CIA director, who interviewed for other positions in the administration, and retired Vice Admiral Robert Harward, who was Defense Secretary James Mattis’s deputy when Mattis led U.S. Central Command. Petraeus would be an interesting pick, since he is a veteran of the Obama administration but was forced to step down and later convicted for sharing classified information with his mistress-biographer.

What did the White House know, who knew it, and when did they know it?

It’s clear that Flynn was not forthcoming with Vice President Mike Pence, as he acknowledged in his resignation letter: “Unfortunately, because of the fast pace of events, I inadvertently briefed the Vice President Elect and others with incomplete information regarding my phone calls with the Russian Ambassador.” The question is how long that was clear. The Washington Post broke the story that Flynn had discussed sanctions with the Russian ambassador to the U.S. prior to inauguration, contrary to his statements. But the Post now reports that then-Acting Attorney General Sally Yates informed the White House counsel, Don McGahn, in January that Flynn was not telling the whole truth about his phone calls, warning that he was vulnerable to Russian blackmail. She also discussed it with FBI Director James Comey, who was initially resistant to informing the White House but later came around, the Post says. (Yates, an Obama appointee, was later fired for announcing the Justice Department would not carry out Trump’s executive order on immigration.)

McGahn has not commented on the report, but if it’s true, that means a high-ranking White House staffer was aware of Flynn’s duplicity long before the public learned of it, late last week. Who, then, did McGahn inform? Did Chief of Staff Reince Priebus know? How about presidential aides Steve Bannon, Jared Kushner, and Kellyanne Conway? Did Trump know? (When asked on Friday, Trump claimed to be unaware of the Post report in which Flynn admitted he may have misled Pence.) Did Pence? If not, why did McGahn not see fit to inform them? If so, what actions did the others take? As late as Monday afternoon, top Trump aides were saying that Flynn had Trump’s full confidence, and hours later, he was out.

Why was Flynn finally pushed, and who goes next?

Much analysis of the White House has adopted the lens of two competing teams—an establishment squad, centered around Priebus, and an insurgent platoon, led by Bannon. Flynn was close to Bannon, but Politico and the Times report that Bannon wanted to fire Flynn as early as Friday, and eventually asked for his resignation. (Bannon’s old outlet, Breitbart, however, blames “establishment forces” for Flynn’s ouster.) The president, meanwhile, was happy to wait and see if Flynn could survive, reports Phil Rucker of The Washington Post. One interesting takeaway is that it was the Bannon team that pushed out one of its own when he became a liability. It’s also somewhat surprising that even when it became clear that Flynn has misled Pence, and allowed him to mislead the American people, he had a chance to survive—a sign of Trump’s reluctance to fire aides, and a curious statement about Pence’s position in the scheme of things.

It’s highly unusual for a high-level official to leave an administration so quickly, within just three weeks. (Sometimes appointees are forced to withdraw before taking their jobs, but effectively never is one installed and then pushed out as rapidly as Flynn.) Last week, I suggested that the Trump administration had begun to look a little like a reality-TV show—Survivor: West Wing. If so, Flynn was the first to fall, but of course there’s always the next round of elimination. So who will be the next to leave the chaotic White House, and will be part of the post-Flynn shakeup, or for different reasons?

Is the FBI still investigating the Trump administration’s ties to Russia?

Once it became clear that Flynn had discussed sanctions with Russian officials, there was speculation that he might have violated the Logan Act, which bars unauthorized citizens from negotiating U.S. policy. But the prospect of a Logan Act prosecution was always highly remote—the bigger story is about the nature of Trump administration contacts with the Russians more generally, and whether Russia interfered with the presidential election to help Trump and hurt Hillary Clinton.

It’s known that the FBI has been investigating these ties: CNN reported in January that the bureau was looking into Flynn’s calls. The Post reports that this was part of a broader investigation. So, is that investigation still ongoing? What else is it considering, and when might the contents become public? And why was Director Comey, who was so quick to publicize developments in the FBI investigation of Hillary Clinton’s private email server, reportedly so reluctant to confront the White House about Flynn’s dissembling? The Army is also, according to the Times, investigating whether Flynn received money from the Russian government for a 2015 trip, which could break the law.

How will the rest of the Republican Party respond?

Between the FBI and Army investigations, it’s clear that there are important unanswered questions about Flynn’s dealings. Yet the Trump administration’s line, somewhat implausibly, is that the “real story” is not the president’s top security aide misleading the vice president and the American people, but instead the leaks that have fed the story—the news about Yates’s call to McGahn, the fact that the FBI was investigating Flynn’s calls, the sources who said Flynn was lying. Breitbart has also taken this line.

How will other members of the president’s party react, though? So far, many of them seem unwilling to get anywhere near the story. Representative Jason Chaffetz, who leads the House Oversight Committee, suggested Tuesday that with Flynn’s resignation, the story was coming to an end. On Monday, Representative Devin Nunes, who leads the House Intelligence Committee, staunchly defended Flynn and said there was no need for him to resign. On Tuesday, Nunes said that his committee would not investigate Trump and Flynn’s conversation, citing executive privilege, but said he wanted the FBI to explain the leak of transcripts of Flynn’s calls. On the Senate side, where GOP members have been more eager to investigate Russian interference in the election, Senator Roy Blunt called for a committee to examine Trump’s ties with Russia “exhaustively” and to question Flynn. It might not be wrong that the intelligence community was out to get Flynn, argues Eli Lake, who points to Flynn’s rocky relationship with spies over time. But whether Republicans in Congress are more interested in Flynn’s dubious dealings with Russia or with the question of leaks that pushed him out will say a lot about their priorities, and whether they are willing to stand up to the White House.