At long last, special counsel Robert Mueller has completed his Trump-Russia report.

If only we knew what it says.

“Special Counsel Robert S. Mueller III has concluded his investigation of Russian interference in the 2016 election and related matters,” Attorney General Bill Barr wrote in a letter to congressional committee leaders Friday.

“The Special Counsel has submitted to me today a ‘confidential report explaining the prosecution or declination decision’ he has reached,” Barr continued. “I am reviewing that report and anticipate that I may be in a position to advise you of the Special Counsel’s principal conclusions as soon as this weekend.”

So, Mueller has completed the lengthy investigation that began nearly three years ago. It’s clearly a major moment in the Russia scandal, but whether it marks the scandal’s end, or the beginning of a new phase in it, isn’t yet clear. It depends on just what the special counsel found.

The completion of a report appears to signal that no new indictments are coming from Mueller. The special counsel regulation says his report should be provided “at the conclusion of the Special Counsel’s work.” In other words, Mueller is done. (Though he may have handed off certain matters to other prosecutors to continue investigating. A Justice Department official told reporters Friday that there are no Mueller indictments that remain sealed.)

All we know about Mueller’s report so far is that, per the regulation governing his work, it should explain “the prosecution or declination decisions reached by the Special Counsel” — that is, why Mueller decided to charge some people but not others.

Another wrinkle is that the regulation says the special counsel report should be “confidential.” This suggests the ball is in Barr’s court now. During his Senate confirmation hearings, Barr said he would do what he could to make as much of Mueller’s findings public as possible. But he left open the possibility that he could keep parts of it secret. This means that so far, we are in the dark on what Mueller found on President Trump and Russia.

There are potentially good reasons for concealing parts of Mueller’s report — the likely use of classified information, the need for grand jury witness secrecy, and Justice Department policy not to opine about uncharged individuals. Democrats, however, fear a potential cover-up, and will put enormous pressure on Barr.

As for what’s next, should the report’s conclusions become known, it really depends on whether Mueller’s findings are damning. If they are, we could be headed for impeachment. But if they’re not, the Trump-Russia scandal may have finally reached its end.

The Trump-Russia investigation began well before Mueller’s appointment

The FBI opened its counterintelligence investigation into the Trump campaign’s ties to Russia back in July 2016 — during the presidential campaign itself.

Earlier that month, emails stolen from the Democratic National Committee had been posted by WikiLeaks. The Russian government was believed to be behind the hack. And the US soon got a tip that one Trump campaign adviser, George Papadopoulos, had professed to know, months before, that Russia had “dirt” on Hillary Clinton. So the FBI opened its investigation, and three other campaign advisers — Paul Manafort, Michael Flynn, and Carter Page — soon came under their scrutiny too.

The probe exploded into public view soon after Trump won. During the transition, then-FBI Director James Comey briefed the president-elect on allegations in an unverified dossier claiming a Trump-Russia conspiracy — and BuzzFeed News then published that dossier. Shortly afterward, Flynn became entangled in the investigation and resigned as national security adviser after only three weeks in the job. Finally, in March, Comey publicly confirmed the investigation in congressional testimony.

A major turning point came when Trump fired Comey on May 9, 2017 — a shocking move, given that the FBI director serves a 10-year term and has traditionally been independent. Trump’s move threw the political system, and particularly the Justice Department, into crisis. Particularly when Trump told NBC’s Lester Holt a few days later, “I decided to just do it; I said to myself, I said, ‘You know, this Russia thing with Trump and Russia is a made-up story, it’s an excuse by the Democrats for having lost an election that they should’ve won.’”

Top FBI officials — aware that Trump had privately pressured Comey to drop the Flynn probe — quickly opened two cases into Trump personally, an obstruction of justice investigation and a counterintelligence probe of his Russia ties. And eight days later, Deputy Attorney General Rod Rosenstein appointed a special counsel to take charge of both: Robert Mueller, who had been Comey’s predecessor as FBI director.

At the time, conservative Republicans said they welcomed the investigation. Rep. Mark Meadows, the conservative chair of the House Freedom Caucus, told Vox’s Tara Golshan at the time, “I think it’s a prudent move. Obviously it shows that the Department of Justice is taking it seriously and when we look at getting to the bottom of this on behalf of the American people.”

Lately, however, Trump and his allies have labeled Mueller’s investigation a “witch hunt.” Depending on what Mueller found out, that assessment could evolve yet again.

What Mueller has done during his investigation

Mueller quickly became one of the most iconic figures of the Trump administration. His appointment brought an end to the crisis Trump had caused by firing Comey and restored confidence that if the president was implicated somehow in the Russia scandal, a highly qualified investigator with an all-star team would now get to the bottom of it. Mueller’s unusual decision to never speak publicly about the investigation only added to his mystique.

Because the special counsel charged a sprawling set of crimes. In the final months of 2017, Mueller won guilty pleas from Papadopoulos and Flynn, both on charges of lying to the FBI about their Russia contacts. He also indicted former Trump campaign chair Paul Manafort and his right-hand man Rick Gates for lobbying and financial crimes — eventually spurring Gates to flip and become a cooperating witness against Manafort and others in Trumpworld.

Mueller then indicted two groups of overseas Russians for interfering with the election — one used social media propaganda, while the other (a group of Russian intelligence officers) hacked leaked Democrats’ emails. After this, he convicted Paul Manafort at trial, which spurred Manafort to plead guilty to avert a second trial in another venue.

Then Mueller revealed a plea deal with former Trump lawyer Michael Cohen, who admitted to lying to Congress about talks to build a Trump Tower in Moscow during the campaign. And he indicted Roger Stone for lying to Congress about his efforts to get in touch with WikiLeaks during the campaign. He’s also been dealing with other matters, like arguments over whether Paul Manafort lied after promising to cooperate, and a court case brought by a mysterious company fighting a grand jury subpoena.

Finally, there’s the question of the president. Mueller probed whether Trump had obstructed justice while in office through his efforts to interfere with the investigation, and examined whether the president himself was involved in any Russian election interference efforts. Trump ultimately refused to agree to a sit-down interview with Mueller, but he did submit written answers to a limited set of questions late last year.

All the while, Trump himself has disparaged the investigation as a witch hunt and denied any wrongdoing. His legal team in 2017 publicly insisted they were cooperating with the probe, but gradually Trump’s posture shifted more toward condemnations of and attacks on Mueller, particularly after the president hired Rudy Giuliani as his lawyer in April 2018.

The end, or the beginning of a new phase?

There has been much chatter in Washington that Mueller was working on some kind of a report that would be the end product of his investigation. Many believed this report would serve to answer the public’s questions regarding Trump and Russia, or lay out a purportedly damning case like the Starr report did for President Bill Clinton.

But we have little idea what such a report would look like, and this is all the regulation in question says about it:

One thing to note here is that the report envisioned by the regulation is meant for the attorney general — not Congress and not the public. It seems not meant for the public, since the report is said to be “confidential.” The only specific information we have on its contents is that it should explain Mueller’s “prosecution and declination decisions,” but the level of detail it will include is not clear.

In any case, the report is now done and in Bill Barr’s hands. The next question will be whether it will be made public in some form. Barr is under no formal obligation to make the report public, but he’ll face immense pressure from congressional Democrats to release as much of the special counsel’s findings as possible. And if the attorney general did try to bottle things up, there are other avenues through which Mueller’s findings can become public — through leaks, or perhaps even congressional testimony by Mueller himself.

But the big question is, of course, what Mueller found. Has he laid out a damning fact pattern implicating the president of the United States in potential crimes? If so, and if that becomes known, House Democrats may well push for impeachment — meaning there will be months more of Trump-Russia drama. But if Mueller did not end up implicating Trump after his long investigation, the political world will likely view that as an exoneration of Trump, and the conclusion of the scandal that’s overshadowed his presidency more than any other.

For more on the Mueller probe, follow Andrew Prokop on Twitter and check out Vox’s guide to the Trump-Russia investigation.