Special counsel Robert Mueller’s sprawling, 22-month investigation has ended with a terse four-page letter from the attorney general — and a whole lot of loose ends.

Foremost among these is the question of when we will get to see more of Mueller’s report itself, rather than just William Barr’s summary. But commentators are already confused and divided on what we can infer from Mueller’s failure to “establish” conspiracy to interfere with the election means, and why Mueller decided not to decide on whether Trump obstructed justice.

More broadly, it’s also unclear how a great many threads Mueller investigated that weren’t mentioned in Barr’s letter were resolved — or unresolved. Congress will try to get answers in the coming days, and here are some of the biggest questions they will have.

The biggest loose end: When will we see (some of) the report?

Of course, the biggest loose end is that we still haven’t seen Mueller’s report itself. We’ve only seen Barr’s summary of it, which does not reveal Mueller’s reasoning or any details, and only quotes the special counsel a handful of times.

Barr wrote Sunday that his “goal and intent is to release as much of the Special Counsel’s report as I can consistent with applicable law, regulations, and Departmental policies.”

The first step in that process, he said, will be identifying what obtained Mueller from his grand jury — because he says grand jury material cannot by law be made public. Barr said materials impacting “other ongoing matters,” such as investigations Mueller referred elsewhere, must also be identified.

It’s unclear how long these steps will take, but once they are completed, we could get a (heavily redacted) Mueller report released. A Justice Department official told reporters Tuesday this will likely take “weeks not months,” but there’s some ambiguity about whether that refers to a redacted version of Mueller’s actual report, or simply another Barr summary with more information. If some version of the report is released, though, there will likely be more political and legal battles about revealing what’s under those redactions.

Did Mueller find nothing on collusion — or just not enough to prosecute?

The special counsel’s decision not to charge Americans with criminally conspiring with the Russian government to interfere with the election has spurred skeptics of the Russia probe to claim vindication. Trump supporters claim this confirms his “no collusion” mantra, and critics of the investigation from both the left and right have acted as if Mueller definitively declared there was nothing here at all.

Other commentators, though, have cautioned against jumping to that conclusion before seeing Mueller’s fuller findings. “Without seeing Mueller’s full report, we don’t know whether this is a firm conclusion about lack of coordination or a frank admission of insufficient evidence,” defense attorney Ken White writes at the Atlantic.

Barr quotes the Mueller report’s exact language twice on this topic. The first quote is, “the investigation did not establish that members of the Trump Campaign conspired or coordinated with the Russian government in its election interference activities.” The second is, “the evidence does not establish that the President was involved in an underlying crime related to Russian election interference.”

So it’s not yet entirely clear whether Mueller’s report describes a murky situation in which there’s some evidence that collusion occurred — or whether this part of the investigation truly did lead nowhere.

What did Mueller find on obstruction — and why didn’t he make a recommendation one way or the other?

On the topic of obstruction of justice, Mueller’s report specifically says it “does not conclude that the President committed a crime,” but that it “also does not exonerate him,” according to Barr. (Barr then proceeded to exonerate Trump himself.)

That, of course, raises the questions of what exactly Mueller found on obstruction. Here, the special counsel is known to have investigated:

The circumstances around Trump’s firing of National Security Adviser Michael Flynn

Trump’s conversations with FBI Director James Comey and his eventual firing of Comey

Trump’s pressures on Attorney General Jeff Sessions over the Russia investigation

Trump’s treatment of and contacts with various other Justice Department and intelligence officials, with regards to investigations implicating him or his associates

Whether Trump or his associates may have hinted at or offered pardons to witnesses in exchange for not incriminating him

False testimony from Trump associates to congressional committees investigating Russian interference

Trump’s involvement in crafting a false public story about Donald Jr.’s meeting with the Russian lawyer

Barr’s letter also says that “most” of the presidential actions Mueller analyzed in the obstruction report have “been the subject of public reporting.” But most is not all, so there appear to be some potentially obstructive Trump actions we don’t yet know about. So what are they?

Then there’s the question about why Mueller couldn’t make up his mind about whether Trump committed a crime here. Barr suggests that Mueller was stymied by “‘difficult issues’ of law and fact concerning whether the President’s actions and intent could be viewed as obstruction.” But he is vague on why, specifically, Mueller “determined not to make a traditional prosecutorial judgment.” Some have suggested that Mueller may have intended to leave the topic to Congress and not Barr — but again, we need to see his fuller report for more information.

What happens to Mueller’s existing cases?

As the special counsel’s office closes down, any pending cases and matters Mueller’s team has dealt with will be handled off to other Justice Department offices to resolve.

For instance, the US Attorney’s Office for the District of Columbia will handle the prosecution of Roger Stone — that office has been involved in Stone’s charges from the get-go, and Stone’s trial is currently scheduled for November 5, 2019.

DC federal prosecutors are also taking over unresolved matters relating to Paul Manafort, Rick Gates (who has not yet been sentenced), and a mysterious company owned by a foreign government that’s been fighting a subpoena. Michael Flynn’s sentencing, and an appeal from an associate of Stone’s who is fighting testimony, will also likely be handed off to other prosecutors.

And at a court hearing on Wednesday, we heard the somewhat surprising news that the grand jury Mueller convened is not only still at work but “continuing robustly.” That news came from a prosecutor from the US Attorney’s Office for DC, which now seems to be in charge of that grand jury.

What happened to ... everything else Mueller investigated?

One surprising aspect of Mueller’s findings on Russian interference with the election, as summarized by Barr, is that they were quite narrowly tailored.

Barr writes that Mueller did not find that any Trump associates conspired or coordinated with the Russian government on the Kremlin’s two main efforts to interfere with the election: the Internet Research Agency’s social media propaganda operation, and the hacking and leaking of Democrats’ emails.

Yet Barr’s summary mentions nothing about ... well, many, many other topics related to the Trump team and Russia that we know Mueller has investigated. These include:

Barr’s summary tells us nothing of what became of Mueller’s inquiries into all these matters. But there are a few possibilities.

1) Dead ends: It’s simply possible that some of the above turned out to be investigative dead ends not worth mentioning in a top-line summary.

2) Included in separate counterintelligence findings: A second possibility ties into how the Russia investigation originated as a counterintelligence probe into whether Trump campaign advisers were working on Russia’s behalf, either wittingly or unwittingly. That probe was eventually expanded to include President Trump himself.

Some of these are not about criminal conspiracy with the Russian government to interfere with the election, which was the focus of Barr’s report. Instead, these are about potential compromise or links to Russia — something that would be part of a counterintelligence probe rather than a criminal one.

So these counterintelligence findings may well have been separated out from Mueller’s main report (which focused on prosecution or nonprosecution decisions), to be handled elsewhere. And indeed, NBC News now reports that congressional leaders may be briefed on Mueller’s counterintelligence findings in the next 30 to 60 days. So stay tuned for more on that.

3) Referred elsewhere to DOJ to investigate: According to Barr’s letter, Mueller “referred several matters to other offices for further action” during his investigation. That is — matters on which the special counsel chose not to bring charges, but on which he think other Justice Department offices might.

We know of some of these. By February 2018, Mueller had referred an investigation into Michael Cohen’s finances to SDNY. And by August 2018, Mueller had referred cases about several people who had worked with Manafort on his Ukraine lobbying work — Tony Podesta, Vin Weber, and Greg Craig — to other offices. However, we don’t know how many matters Mueller referred elsewhere or what those offices might do with them moving forward.

What is Congress going to find out?

Probably before that is done, Barr will end up testifying before Congress. He has a scheduled appearance before an appropriations subcommittee to talk about the Justice Department’s budget on April 9. But Democrats want him to testify before the House Judiciary Committee before that to answer questions about the Mueller investigation, and are currently trying to nail down the timing.

Additionally, as mentioned above, the FBI is expected to brief key congressional leaders and committee chairs on the findings of the counterintelligence investigation into whether Trump or his campaign advisers were working on Russia’s behalf, per NBC News. That briefing would happen behind closed doors, but information from it could leak.