Paul Manafort’s trial in Alexandria, Virginia, captured most of the nation’s attention this week, but legal proceedings across the Potomac River in Washington may be the best indicator of where the Russia investigation is going next.

Special counsel Robert Mueller’s team questioned Kristin Davis, the so-called Manhattan Madam, before a grand jury at the D.C. federal courthouse on Friday. Mueller is reportedly probing her connections with veteran GOP political operative Roger Stone. Elsewhere in the building that same day, a federal judge held Andrew Miller, another Stone associate, in contempt of court for refusing to obey a grand-jury subpoena also issued by Mueller for his testimony.

It’s increasingly apparent that Stone, a political dirty trickster and occasional adviser to President Donald Trump, may be in serious legal jeopardy. Stone himself told NBC’s Meet the Press in May that he is “prepared” to be indicted by Mueller. In the interview, he suggested that the charges could be related to his business operations instead of Russian electoral interference. “It is not inconceivable now that Mr. Mueller and his team may seek to conjure up some extraneous crime pertaining to my business, or maybe not even pertaining to the 2016 election,” Stone told moderator Chuck Todd. “I would chalk this up to an effort to silence me.”

For what, exactly, would Mueller indict Stone? As with many things surrounding the Russia investigation, the answer isn’t quite clear. Two potential avenues are emerging from the witnesses that Mueller has already subpoenaed and the question that he’s reportedly asked them. If Stone is indicted on charges related to his super PAC or for other business dealings unrelated to foreign election meddling, the political impact could be minimal at first. If, on the other hand, the charges pertain to Russian cyberattacks, it would mark a major shift in the Russia investigation.

Mueller’s operations are largely hidden from public view, making it hard to gauge his progress in the Russia investigation. At the same time, he and his team appear to be taking a heightened level of interest in Stone’s activities. Mueller’s team has called at least a half-dozen Stone aides and confidants before the grand jury this year, often in addition to the more standard interviews with FBI agents. Stone has told reporters that he himself hasn’t been contacted by the special counsel yet, a silence that could indicate he is a target of the investigation.