The 448-page Mueller report has been public for two months, so it might seem strange that the Justice Department’s original instructions to special counsel Robert Mueller, outlining what he was assigned to investigate, are still a secret. But they are. And now, it turns out those instructions were more extensive than previously known. Until now, it was widely understood that there had been two “scope memos” from the DOJ to Mueller. Now, it turns out there was a third, as well.

When Mueller was first appointed, on May 17, 2017, the appointment document, signed by Deputy Attorney General Rod Rosenstein, authorized Mueller to investigate three areas: “i) any links and/or coordination between the Russian government and individuals associated with the campaign of President Donald Trump; ii) any matters that arose or may arise directly from the investigation; [and] iii) any other matters within the scope of [obstruction of justice laws].”

That document was made public immediately. It shaped the popular understanding of what Mueller was investigating. It was, however, just for show.

On April 3, 2018, news broke that Rosenstein wrote a second scope memo to Mueller. Dated Aug. 2, 2017, just 10 weeks after the original appointing document, the second scope memo came to light as a result of court proceedings for the trial of former Trump campaign chairman Paul Manafort. But most of it was blacked out. Still, the public could see that Rosenstein wrote that the original May 17, 2017 scope memo “was worded categorically in order to permit its public release without confirming specific investigations involving specific individuals. This [Aug. 2] memorandum provides a more specific description of your authority.”

Rosenstein apparently went on to list several assignments, but only one was not blacked out. In that section, Rosenstein authorized Mueller to investigate allegations that Manafort “committed a crime or crimes by colluding with Russian government officials with respect to the Russian government’s efforts to interfere with the 2016 election for President of the United States, in violation of United States law,” as well as allegations that Manafort “committed a crime or crimes arising out of payments he received from the Ukrainian government before and during the tenure of President Viktor Yanukovych.”

Whatever else Rosenstein told Mueller remains secret to this day.

Now, there is more. The Justice Department has recently allowed members of some congressional committees to view the scope memos, and out of that has come the news that there was a third scope memo to Mueller. Dated Oct. 20, 2017, its contents remain a secret. But its very existence suggests something was going on behind the scenes in the relationship of Mueller and his supervisors at the Justice Department.

Was Mueller heading off in new directions, with Rosenstein belatedly giving him authorization to proceed? Was Mueller proposing to investigate people or events not known when he was originally appointed? Was there something else?

At the moment, the third scope memo, like most of the second scope memo, remains a secret. Mueller included a brief description of it in his report, revealing that Rosenstein reauthorized him to investigate Michael Cohen, Richard Gates, and Roger Stone “as part of a full and thorough investigation of the Russian government’s efforts to interfere in the 2016 presidential election.” But the report, as released, blacked out other names on the grounds of “personal privacy.” It is not clear what parts of the investigation they represented, and it is not clear why a third scope memo was necessary in the first place.

Most of all, it is not clear whether all that secrecy is warranted. Perhaps the memos concern matters that are still ongoing that need to remain under wraps. On the other hand, Mueller announced that his investigation into conspiracy and coordination between Russia and the Trump campaign — the core area of his jurisdiction — was over and done. “The office has concluded its investigation into links and coordination between the Russian government and individuals associated with the Trump campaign,” the Mueller report said.

It seems safe to say the memos will one day be released, but it is not at all clear when that will be. The public needs to know the story, not only of the Trump-Russia issue but of the Trump-Russia investigation.