You can add the Supreme Court’s chief justice to the list of high-powered judges now engaged in refereeing a mysterious legal fight that’s captivated Washington since October.

An unnamed company owned by a foreign government is defying a subpoena for information reportedly linked to special counsel Robert Mueller’s Russia probe into Russian efforts to influence the 2016 election. On Sunday, Chief Justice John Roberts got involved, issuing a temporary pause to a lower court’s ruling that had placed the unnamed corporation in contempt and slapped it with a financial penalty. Justice Roberts ordered that an additional briefing on the matter be presented by noon on Dec. 31.

The case could provide the first opportunity for the Supreme Court to make its presence felt on the Russia investigation.

While key details remain obscure, the standoff has escalated quickly all the way to the high court — igniting intense speculation about what the fuss is about.

Here's what we know about the dispute:

Secret from the start

The case has been winding its way through the legal system since August, under the cover of extreme secrecy. The standoff burst into public view in October, when a Politico reporter hanging out in the D.C. Court of Appeals’ clerk’s office overheard a lawyer request a copy of the special counsel’s latest sealed filing so his law firm could respond.

The special counsel has refused to confirm its involvement, although a lot of circumstantial details collected by reporters since then comprise mounting evidence that it is.

When curious D.C. journalists attempted to learn more by snooping around the sealed courtroom during oral arguments on Dec. 14, authorities responded by shutting down the entire fifth floor of the building.

A ruling subsequently released by a three-judge panel on Dec. 18 revealed a few concrete details, and finally killed off swirling speculation that the case might relate to a secret subpoena for Trump himself to come and testify.

The case involves a prosecutor attempting to obtain “information” from a company owned by a foreign country, the judges confirmed.

The company has tried to argue that granting the request would mean breaking the law in its home country. The judges ruled that assertion wasn’t well-supported, and upheld a lower district court’s decision to impose a monetary fine for every day the company refuses to hand over the info.

The judges likewise denied the company’s arguments that the U.S. Foreign Sovereign Immunities Act (FSIA) effectively means that it can’t be sued, citing a commercial activity exception — and denied the corporation’s claim that the D.C. district court lacked jurisdiction.

“COUNTRY A”

This secretive court battle wouldn’t mark the first time a foreign company has been drawn into the Mueller probe.

In February, Mueller indicted three Russian companies for allegedly running a sweeping online effort aimed at influencing the 2016 election via social media. One of the companies, Concord Management and Consulting, lawyered up and mounted a vigorous defense of itself against Mueller’s accusations in court that continues to this day.

Concord is run by Yevgeny Prigozhin, the catering tycoon so close to Russian President Vladimir Putin that he’s known by the nickname “Putin’s Cook.”

If Mueller is indeed behind the subpoena, a Russian-owned entity would be the most obvious explanation, given the special counsel’s mandate to probe Russian influence, but other countries have also been tied to the investigation.

In March, The New York Times reported that Mueller had pressed witnesses about any possible attempts by the United Arab Emirates to buy political influence by directing money to support Trump during the campaign. In April, The Wall Street Journal reported Mueller had been asking questions about a private consulting firm that’s undertaken projects for the Emirates.

Earlier this month, the Daily Beast reported that Mueller is expected to issue new court filings about Middle Eastern countries’ attempts to influence American politics.

“Various witnesses affiliated with the Trump campaign have been questioned about their conversations with deeply connected individuals from the United Arab Emirates, Saudi Arabia, and Israel, according to people familiar with the probe,” the outlet wrote.

Until more details come to light, the guessing game will continue, even as the case catches the attention of the highest court in the land.