One tip-off was in Michael Flynn’s December 1 “allocution”—his signed submission to the court as part of his guilty plea to making false statements to the FBI on January 24, 2017. It received almost no media attention but suggested the nature of the criminal conspiracy that would likely be at the heart of Mueller’s prosecution.

Flynn didn’t just vaguely admit he lied. The law doesn’t allow that. He admitted in writing that his lie “had a material impact” on the FBI’s probe “into the existence of any links or coordination between individuals associated with the [Trump] Campaign and Russia’s efforts to intervene in the 2016 election.”

The conspiracy case–the heart of Mueller’s efforts– almost certainly boils down to an old-fashioned quid pro quo. Flynn’s “quid”—the substance of his recorded conversations with Russian Ambassador Sergey Kislyak— was lifting the sanctions that President Obama imposed on Russia in late 2016 and the earlier sanctions related to Russia’s invasion of the Ukraine. The “quo” was collusion (“conspiracy” in legal terms) with Russians to harm Hillary Clinton’s 2016 campaign, which Flynn effectively admitted was “material” to his lies after the election. Anyone associated with this deal is in deep legal trouble.