As Robert Mueller’s investigation into Russian interference churns on, the list of individuals the special counsel hasn’t interviewed is arguably as interesting as those he has. And given his communications with WikiLeaks and Russian hacker Guccifer 2.0, professional ratfucker and longtime Donald Trump confidant Roger Stone ranks near the top. Stone has yet to be called in for questioning himself, but reports suggest Mueller has taken an interest in Stone, probing said WikiLeaks links, as well as his relationship with Rick Gates, the former deputy chairman of the Trump campaign who’s cooperating with the government. And at the end of last week, Mueller’s escalating probe engulfed two more known Stone associates: Randy Credico, a comedian and radio-show host, and “Manhattan Madam” Kristin Davis, a former employee and close friend of Stone’s, adding to a growing list of people in the Republican operative’s orbit to come under the microscope of the F.B.I.

The role of Credico in the Russian melodrama that has captivated Capitol Hill for the past two years is a curious one. Stone has claimed that Credico gave him information from WikiLeaks founder Julian Assange, who appeared on the latter’s radio show, about plans to release hacked e-mails from the Hillary Clinton campaign and the Democratic National Committee. Of course, true to form, Stone’s account has shifted over time. In August 2016, Stone said, “I actually have communicated with Assange.” Months later, Stone walked back this assertion, claiming that a “journalist”—whom he later identified as Credico—acted as an “intermediary” between him and the WikiLeaks founder. Then, in September 2017, Stone’s lawyer told the Senate Intelligence Committee, “Mr. Stone concedes that describing Credico as a go-between or intermediary is a bit of salesmanship.” Credico, meanwhile, has maintained that he did not act as an information broker between the two, but simply directed Stone to Assange’s public statements. (Stone has denied any wrongdoing.)

Regardless, Credico’s involvement has long piqued Mueller’s interest. After Credico rejected a request for a voluntary interview, the special counsel subpoenaed the radio-show host for a grand jury interview on September 7, according to his lawyer, Martin Stolar. Stolar told CNN that it is unclear what Mueller seeks from Credico, but speculated, “They probably want to talk to him about Roger Stone and Julian Assange.” Citing two sources familiar with the matter, Mother Jones reported Monday that investigators are also reviewing a batch of e-mails Stone sent Credico after the latter disputed his claims about the contacts with WikiLeaks—specifically, the special counsel is reportedly interested in the extent to which Credico interpreted them as threats. “I am so ready. Let’s get it on. Prepare to die cock sucker,” Stone reportedly wrote to Credico in an e-mail dated April 9.

In a series of text messages to M.J., Stone said that his e-mails were “laced with a consistent theme that [Credico] should stop lying and tell the truth,” and that “If he is compelled to testify I would urge Mr. Credico to simply tell the truth. Any deviation from these facts as stated would be perjury which I could easily prove.” Stone’s posturing, while not out of character, could be a tell: if Credico truly did not act as a conduit, his testimony could prove detrimental to Stone, raising further questions about what role Stone played in Russia’s effort to derail Clinton’s candidacy. Those questions are particularly apt given the questionable contacts Stone made during the campaign: in May 2016, he met with a Russian national, Henry Greenberg—who has also gone by the name Henry Oknyansky—in Florida on the pretense that he would be provided “damaging information” on Clinton for $2 million. (Stone has since claimed that the meeting was an F.B.I. sting operation, and said he omitted it from his Congressional testimony because he forgot about it.) In his indictment of a dozen Russian operatives last month, Mueller specifically mentions “a person who was in regular contact with senior members of the presidential campaign of Donald J. Trump,” who exchanged messages with Russian hacker “Guccifer 2.0”—Stone himself has admitted that he is “probably” the person to whom the document refers.

After testifying before Mueller’s grand jury, Davis said she does believe that Mueller is closing in on Stone, who ran her ill-fated 2010 New York gubernatorial bid. “I think they’re concerned with all of the people in the 2016 campaign, all of the high-profile names that we’ve seen come across and all of the people that have worked for Roger,” she said during an interview with CNN on Monday night. As to what specifically she thinks investigators are probing, Davis highlighted Stone’s highly scrutinized Podesta tweet, which seemed to foretell WikiLeaks’s release of the Clinton campaign chairman’s hacked e-mails. “I think there’s the general concern for some things that he seemed to predict,” she told host Chris Cuomo. When and if Mueller will come calling for Stone remains a mystery. But Credico and Davis are two of more than a half dozen Stone associates who have or will face off with the special counsel, according to M.J. And the special counsel appears intent on speaking with those in Stone’s orbit—on Friday, a D.C. district judge held former Stone aide Andrew Miller in contempt for his refusal to testify.