Special Counsel Robert Mueller is reportedly focused on a “series” of late-night phone calls allegedly made between then-candidate Donald Trump and then-adviser Roger Stone during the 2016 presidential election campaign.

According to The Washington Post, the caller ID identified Trump’s calls–which usually came during the wee wee hours–as emanating from an “unknown” number. Stone, however, apparently knew to pick up.

The Post‘s report notes:

Those nocturnal chats and other contacts between the man who now occupies the Oval Office and an infamous political trickster have come under intensifying scrutiny as special counsel Robert S. Mueller III’s investigation bores into whether Stone served as a bridge between Trump and WikiLeaks as the group was publishing hacked Democratic emails.

The draft statement of offense for conspiracy theorist Jerome Corsi released earlier this week appears to provide some amount of connective tissue between Trump, Stone, Corsi, and WikiLeaks. It is believed that WikiLeaks released material harmful to the presidential campaign of Hillary Clinton after that material was stolen by Russian intelligence officers. Allegations that WikiLeaks directed or took part in the theft of such material has been a matter of inquiry for the press and Mueller team alike.

“[Corsi] said that in the summer of 2016 an associate … who Corsi understood to be in regular contact with senior members of the Trump Campaign, including with then-candidate Donald J. Trump, asked Corsi to get in touch with Organization 1 about materials it possessed relevant to the presidential campaign that had not already been released,” the document made public by Corsi reads.

All indications suggest that the unnamed associate mentioned in the draft statement of offense is none other than Stone. Taken in tandem with the Post‘s Wednesday night report, it appears that Mueller is taking seriously what, if anything, candidate Trump knew about the alleged Stone-Corsi-WikiLeaks nexus.

Earlier this year, the Trump Organization turned over records that detail several calls between then-candidate Trump and Stone during the 2016 campaign. But in comments to the Post, Stone said those voluntarily shared call logs aren’t full records of his conversations with the eventual president because Trump would occasionally call him from other people’s phones.

For their part, both Stone and WikiLeaks have stated that neither party worked together during the 2016 campaign. Trump, by way of his attorneys and in written answers provided to the special counsel’s office last week, said that he had no prior knowledge of WikiLeaks’ bombshell disclosures and that Stone never kept him apprised of the matter, according to the Post‘s sources with knowledge of Trump’s answers.

In comments to the Post, Stone appeared to brush off the implications of Mueller taking a microscope to his late-night calls with the man who would become the 45th president of the United States.

“Unless Mueller has tape recordings of the phone calls, what would that prove?” Stone asked rhetorically.

[Image via Mark Wilson/Getty Images]

Follow Colin Kalmbacher on Twitter: @colinkalmbacher