By Elie Honig

(CNN) -- Special Counsel Robert Mueller filed a two-part sentencing memo for Michael Flynn on Tuesday night. The memo is heavily redacted, leaving much to the imagination, but it confirms that Flynn provided Mueller with valuable inside information on multiple ongoing criminal investigations, including Mueller's core investigation of whether Russian officials colluded with members of the campaign of President Donald Trump.

Think of the memo like a movie trailer: you watch it and think, "I don't know exactly what this is going to be about, but it's definitely going to be good." Bottom line: Mueller still has many more revelations to drop, and they're going to land hard.

In part one of the sentencing submission, Mueller meticulously lays out the details of Flynn's crimes, which Mueller deems "serious." Most importantly, Flynn lied to the FBI about conversations in which he asked Russian ambassador Sergey Kislyak to refrain from escalating the Russian response to sanctions imposed by then-President Obama because of Russian interference in the 2016 election.

Despite Flynn's serious crimes, Mueller asks the court to impose a minimal sentence -- "a sentence at the low end of the guideline range -- including a sentence that does not impose a term of incarceration -- is appropriate and warranted."

Mueller's memo makes this recommendation primarily because of Flynn's "substantial assistance to the government." I've handled dozens of federal cooperators and I have at times specifically requested no jail time -- but only for those who cooperated promptly, fully, truthfully and productively. A sentence of no jail time here is within the sentencing guidelines range of 0 to 6 months but, notably, Mueller did not seek no jail time for less valuable or more problematic cooperators including George Papadopoulos (for whom Mueller requested up to six months in jail -- and who was sentenced to 14 days of imprisonment) and Paul Manafort (whose cooperation collapsed altogether, which Mueller is due to detail in another filing due on Friday).

Indeed, in part two of the submission, Mueller informs the court that Flynn's cooperation was "substantial," and "particularly valuable." Having whet the reader's appetite, however, Mueller then proceeds to offer up a sea of black redaction ink. But Mueller also offers several important clues about what Flynn has done, and what is still to come.

First, Mueller tells the court that Flynn has cooperated on "several ongoing investigations." Every word of that phrase matters: Mueller has used Flynn's information on multiple investigations, and those investigations are not yet over.

So whatever fruits Flynn gave to Mueller -- and we know Flynn gave a lot, because Mueller discloses that his team and other federal prosecutors met with Flynn for a whopping 19 interviews -- Mueller has not fully harvested them yet.

As Mueller puts it, "some of that benefit [from Flynn's cooperation] may not be fully realized at this time because the investigations in which he has provided assistance are ongoing." Translation: people are going to get charged based on Flynn' s information, but not just yet.

Mueller offers other enticing clues about the nature of those ongoing investigations. It appears that Flynn has contributed to three distinct investigations: (1) an investigation of "interactions between the [Trump] transition team and Russian government officials," including the dealings of Flynn and potentially others with Kislyak over sanctions; (2) Mueller's core "investigation concerning any links or coordination between the Russian government and individuals associated with the campaign of President Donald J. Trump;" and (3) another mystery case.

Mueller's description of the mystery case, at section I.A of part two of the submission, begins with "The defendant has provided substantial assistance in a criminal investigation" -- followed by 22 lines of black redaction ink. There simply is no way to know who or what this investigation is about. But we do know that it is separate from the investigation of Russian election interference; that it is ongoing; and that Flynn provided information to Mueller about it. If Mueller deemed the mystery case worth including in Flynn's sentencing memo, it likely is an important one.

Mueller then provides some hints about Flynn's cooperation on the Russian election interference investigation. First, we now know that Flynn did have at least some information about Russian election interference and "links of coordination between the Russian government and individuals associated with the Trump campaign." That in itself is noteworthy: Flynn, who held influential and high-ranking positions in the Trump campaign and the early days of the administration, has provided Mueller with information about collusion between Russia and the Trump campaign.

Just as the reader begins to lean in to read the details of Flynn's cooperation on election interference, however, Mueller offers up 31 lines of redaction interrupted only by the phrase "[t]he defendant also provided useful information concerning." So we do not know precisely what Flynn has told Mueller about collusion between Russia and the Trump campaign -- but we know he has told Mueller something, and likely quite a bit.

Mueller has shown a knack for conveying much important information in few words. Those 31 lines of redactions from Mueller could obscure extensive information about Russian election interference, and could spell the death of Trump's "no collusion" refrain.

Mueller offers one final clue in his closing paragraph when he notes that Flynn's cooperation "was particularly valuable" because he provided "long-term and firsthand insight regarding events and issues under investigation" by Mueller's team. The word "firsthand" is important because it means that Flynn was a direct eyewitness to the events he described to Mueller -- whereas less valuable cooperators sometimes offer only secondhand, hearsay or background information. Flynn was actually in the room for the events he described to Mueller, and not merely a second-tier witness peddling rumors and say-so.

So we do not yet know everything about Flynn's cooperation and indeed the heavy redactions hide nearly all the details that Mueller provided to the court. But, if you read around all that black ink, Mueller did say enough to let us know this: Flynn gave up the goods, and Mueller's work is far from over.

Correction: An earlier version of this article incorrectly described Russian government officials as campaign officials.