Robert Mueller is nothing if not deliberate. When he was investigating the N.F.L.’s handling of the Ray Rice domestic-violence scandal in 2014, Mueller accounted for each of the 1,583 telephone calls made to and from the league’s headquarters during the time period relevant to his probe. As Wired’s Garrett M. Graff recently noted, however, Mueller’s conclusions were frustratingly narrow. Despite trawling a sea of data—5 pages of his 96-page report were dedicated to the N.F.L. mail room’s procedures—Mueller refused to issue a conclusion about the the culture of the N.F.L., its pursuit of justice, or its long suspected inclination to manage its largest crises with a lack of transparency. Instead, he focused narrowly on the precise case in front of him. Now, with Mueller expected to turn over his confidential findings in the Russia investigation to Attorney General William Barr in the impending weeks, some wonder whether the special counsel will remain similarly disciplined, or if he will widen his aperture. (A judge dismissed domestic-violence charges against Rice.)

Clues abound. Mueller may indeed be writing his report in plain sight before our very eyes. As The Washington Post’s Philip Bump noted last week, his team has already composed and released nearly 300 pages of plea deals, indictments, and shadowy details regarding the behavior of Trump grifters like Paul Manafort, Rick Gates, and George Papadopoulos. The details have often been scintillating, in part, because Mueller has generally employed in his filings a litany of “speaking indictments”—a colloquial term that is applied when a prosecutor offers greater detail than necessary to prove their charges. In his indictment of the Internet Research Agency, the Russian troll farm behind the 2016 election disinformation effort, Mueller included the details of a hoax that Russian operatives played on an unwitting U.S. citizen. In his subsequent indictment of 12 G.R.U. intelligence officers, he detailed with remarkable specificity their Internet searches during one 37-minute window. Perhaps the most curious detail comes elsewhere in the G.R.U. indictment, when Mueller notes how one particular spear-phishing attempt aimed at the Hillary Clinton campaign was both a “first time” effort, and conducted “after hours.” These may seem like bread crumbs to a popular audience, but they’re more significant Morse-code tappings to jurisprudential scholars, suggesting that the hackers’ strategy could have shifted at a crucial moment.

Mueller may be deliberate, but he’s not necessarily straightforward. As his investigation appears to draw to a close, the key to understanding his intentions relies not only on examining the information he has included in previous filings, but also upon considering the information that he appears to have omitted, or redacted, from them. Mueller’s 24-page indictment of Roger Stone, issued in January, revealed that the self-described dirty trickster encouraged radio host Randy Credico “to do a ‘Frank Pentangeli’”—a reference to a character in The Godfather: Part II, who lied to Congress only after his mobster brother showed up in the courtroom. But Mueller, the former Marine, also included numerous vagaries in the document. He outlined a series of cases where Stone was in contact with Trump campaign officials about WikiLeaks’ plans to release stolen e-mails, but did not identify said officials, in accordance with D.O.J. policy. Resultantly, we are left guessing the identity of the person who “directed” an unnamed “senior Trump campaign official “to contact Stone about any additional releases and what other damaging information [WikiLeaks] had regarding the Clinton Campaign.” In the end, the filing prompted nearly as many questions as it answered.

Mueller also dedicated much of the January indictment to unraveling the various lies that Stone told about his contacts with Credico, WikiLeaks founder Julian Assange, and conspiracy theorist Jerome Corsi. But the special counsel did not explicitly say whether Stone, Credico, or Corsi were ever actually in contact with WikiLeaks or Assange about the stolen e-mails. In a court filing three weeks later, Mueller at least partially addressed this issue. After previously describing Stone’s attempts to contact Assange through hapless go-betweens, the special counsel’s team said for the first time that it “obtained and executed dozens of search warrants on various accounts used to facilitate the transfer of stolen documents for release, as well as to discuss the timing and promotion of their release.” Consequently, prosecutors wrote, “Several of those search warrants were executed on accounts that contained Stone’s communications with Guccifer 2.0”—the Russian entity that hacked the Democratic National Committee—“and with Organization 1,” a.k.a. WikiLeaks. In other words, Mueller has the receipts when it comes to Stone’s contacts with Guccifer 2.0 and WikiLeaks. What is unclear is the substance of these contacts, and whether they are limited to what is publicly known.

What knowledge did Stone have about the Russian hacking operation and WikiLeaks’ e-mail dumps? Did he share it with the Trump campaign? Mueller is vague about the timing of the Russians’ September 2016 hack, when they successfully gained access to D.N.C. computers, and whether it is related to a Twitter exchange between Stone and Guccifer 2.0 that same month. Nor does Mueller explain what prompted that first spear-phishing attempt on or about July 27, 2016, the same day that Trump called on Russia to hack Clinton’s e-mails. (“Russia, if you’re listening, I hope you’re able to find the 30,000 e-mails that are missing.”) Between the plain text of his filings, however, lie indications that Mueller may have these answers. If you re-read charging documents from the special counsel’s office—both what has been included and what hasn’t—the series of outcomes narrows considerably. These are the known unknowns of the Mueller probe. And while there may not be any one smoking gun in the Russia investigation, it could become a mushroom cloud left for Congress to litigate.

The White House has taken comfort in the fact that among the 37 people and three companies that have been publicly indicted or pleaded guilty in the Mueller probe, not a single Trump associate has been indicted for anything involving a conspiracy to rig the 2016 election or conspire with a foreign government. Indeed, most of the crimes have been so-called process crimes, like lying to the F.B.I. But for those familiar with Mueller’s career—as assistant attorney general for the D.O.J.’s criminal division, as a U.S. attorney in Boston and San Francisco, and later as director of the F.B.I.—these charges are a hallmark of Mueller’s approach to flipping criminals, such as when he cut a deal with Salvatore “Sammy the Bull” Gravano to bring down the Gambino criminal family in the early 1990s.

That strategy isn’t lost on some Trump allies. “This investigation is a classic Gambino-style roll-up,” a source close to the White House observed in November 2017, as the probe was heating up. This approach has also created immense political uncertainty surrounding the outcome of his final report. In the G.R.U. indictment, for instance, prosecutors for the special counsel’s office wrote that Russian intelligence officers “knowingly and intentionally conspired with each other, and with persons known and unknown to the Grand Jury” in order to interfere with the 2016 election. Does the fact that Mueller hasn’t charged those “known and unknown” people mean that he can’t make his case, or that he’s just been working his way up the food chain?

Untruth is endemic to Trumpworld, but the frequency and brazenness of the lies told about Russia strongly suggest that Mueller’s past indictments form the building blocks of a broader conspiracy. Take, for example, the case of Trump’s former national-security adviser Mike Flynn. In December 2017, Flynn pleaded guilty to a single count of lying to the F.B.I. about his contact with the Russian ambassador during the transition. Flynn’s sentencing memo was one of Mueller’s more frustrating court filings. The document notes that the national-security adviser provided “substantial assistance” to the Justice Department during 19 interviews. It also notes specifically that “the defendant provided firsthand information about the content and context of interactions between the transition team and Russian government officials.” The precise details, however, were redacted entirely. Even more mysterious, in December a federal judge postponed sentencing Flynn—Mueller had recommended zero to six months in prison—so that Flynn might continue cooperating with prosecutors.

Then you have Michael Cohen, the president’s longtime personal attorney and fixer, whose case Mueller handed off to the U.S. attorney’s office for the Southern District of New York. In August, Cohen pleaded guilty to crimes including campaign-finance violations stemming from hush-money payments made to two women. In November, Cohen also pleaded guilty to lying to Congress about the Trump Tower Moscow project, which Trump—the infamous “Individual 1” in the S.D.N.Y.’s case—pursued well into 2016 election. Cohen told the court that he lied about the end of Trump Tower negotiations “to be consistent with Individual 1’s political messaging and out of loyalty to Individual 1.” As a reward for his cooperation, Mueller recommended that Cohen receive no additional jail time beyond the recommendation of the S.D.N.Y., although he was ultimately sentenced by a federal judge to three years in prison.

Manafort’s own aborted cooperation agreement with the special counsel provides yet another window into Mueller’s strategy—and, potentially, into whatever conspiracy he may be hoping to uncover. Thanks to a botched redaction, we learned that the special counsel accused Manafort of breaching his cooperation agreement by, among other things, lying about contacts with the Trump administration after the election, as well as discussing a Ukrainian “peace plan” and sharing private polling data with Konstantin Kilimnik, a suspected Russian intelligence agent. In a hearing to discuss the breached agreement, defense attorney Richard Westling argued that Manafort’s lies were only related to a “small set” of topics. “Many of the more sensitive topics that we’re aware of from a—all of us paying attention to what’s gone in the news cycle over the last many months, you know, are things where these issues didn’t come up, where there wasn’t a complaint about the information Mr. Manafort provided,” he said, suggesting his client may have supplied useful information to Mueller that has yet to be made public.

In her ruling on the matter, U.S. District Judge Amy Berman Jackson said that Manafort’s behavior, especially pertaining to his interactions with Kilimnik, was “at the undisputed core of the Office of Special Counsel’s investigation” into whether any Trump campaign officials coordinated with the Russians to derail Clinton’s candidacy. “Mr. Kilimnik doesn’t have to be in the government, or even be an active spy to be a link,” she said. Nor was Jackson convinced that Manafort’s inaccurate statements were unintentional. Over and over, she said, Manafort’s lies revolved around “Kilimnik, Kilimnik, and Kilimnik.” (Mueller previously estimated that Manafort could receive between 19 and 24 years in prison, based on sentencing guidelines. Prosecutors have argued that Manafort lied, at least in part, to “augment his chances for a pardon.”)

And then there’s the perplexing, and still unexplained, role the president played in crafting the misleading statement to The New York Times about the June 2016 Trump Tower meeting attended by Donald Trump Jr., Jared Kushner, Manafort, and a group of Kremlin-linked Russians. The initial statement, dictated by Trump, said the primary purpose of the meeting with to discuss “a program about the adoption of Russian children”—the same subject that Trump said he and Vladimir Putin discussed when they huddled on the sidelines of the G20 summit in July 2017. Of course, later it was revealed that Don Jr. was lured by the promise of Russian government “dirt” on Clinton.

Critics of the Mueller probe argue that such misstatements were accidental or trivial, and that the special counsel’s office is abusing its power by prosecuting lies. But in nearly every case, the topic is the same: Russia. If Flynn’s conversations with then-Russian ambassador Sergey Kislyak were standard fare during a presidential transition, why did he lie to the F.B.I. and multiple administration officials, including Mike Pence, about them? If Trump’s dealings with Russia to build Trump Tower Moscow were appropriate, why did he and Cohen lie about them for more than two years? Why did the president issue a misleading statement on the Trump Tower meeting if it was all aboveboard? If Stone had nothing to hide about his interactions with Guccifer 2.0 and WikiLeaks, then why did he lie about them to Congress and go so far as to threaten to steal Credico’s therapy dog? Why did Papadopoulos lie about the mysterious Maltese professor who told him about the Clinton “dirt”? And why would Manafort breach his cooperation deal with Mueller, risking the rest of his life behind bars, to conceal his interactions with Kilimnik?

Throughout the Russia investigation, Mueller has been unsparing in drilling down to the details in his indictments. And yet, all of these omissions go to the heart of the collusion question. It’s safe to assume that Mueller has the answers, and then some—he has merely chosen not to share them yet. In order to catch all these Trump associates in their lies, Mueller must know the truth. There is the possibility that the special counsel will unveil these answers in a broad conspiracy indictment. Or he could package all the evidence and testimony gathered in the jury process—sans analysis or judgment—and drop the whole thing at the feet of House Speaker Nancy Pelosi, just as Watergate special prosecutor Leon Jaworski did when he sent lawmakers a 55-page grand-jury report known as the “Road Map.” Anyone who looks could see the dots. All that’s left would be to connect them.

As the White House has pointed out following each of Mueller’s indictments, neither the president nor his deputies have been charged with taking part in a foreign conspiracy to illegally influence the 2016 election. At least not yet. Trump himself is almost certainly immune to prosecution while he is president, according to long-standing Justice Department guidelines. But that doesn’t mean Mueller isn’t building a case that he can effectively turn over to Congress, which has the power to impeach Trump. As Asha Rangappa, a former F.B.I. counter-intelligence agent who worked under Mueller, explained to me last year, “Collusion does not necessarily have to be criminal.” The definition of collusion, she continued, could be as simple as “secretly conspiring or working with a foreign power to help them in their covert operation.”

Trump’s lawyers have recognized this. For months, the official position of the Trump White House was that there was “no collusion.” More recently, however, the president’s lawyers have shifted the goalposts. “If Roger Stone gave anybody a heads-up about WikiLeaks’ leaks, that’s not a crime,” Rudy Giuliani told ABC News in December, several weeks before Mueller’s indictment against Stone revealed that the longtime Trump confidant had communicated with campaign officials about WikiLeaks’ plans. “The crime is conspiracy to hack. Collusion is not a crime; it doesn’t exist.”

In the realm of impeachment, collusion is indeed a political question. But whether Trump, his campaign, or his associates conspired with the Russians to sabotage Clinton and subvert the American electoral process is a legal one. When analyzing the public body of Mueller’s work, the litany of speaking indictments and other court documents suggest that Mueller is building toward something big. As Glenn Kirschner, a former federal prosecutor who worked closely with Mueller, posited to me last year, “It wouldn’t be a surprise if he returned a large conspiracy indictment for basically a conspiracy to defraud the United States by interfering in our elections.”

With the two-year anniversary of Mueller’s appointment this spring, some of the juiciest—and arguably most consequential—questions about Russian election interference and the Trump campaign remain unanswered. But every bizarre detail or curious omission from Mueller to date could be a bread crumb leading to what the special counsel is preparing next. The investigation’s known unknowns are an investigative road map.

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