What special counsel has offered publicly signals long year ahead in Russia probe

The special counsel's investigation will run into the new year.

However, the status of Mueller's probe has remained elusive as so much of what his investigators are up to is done in secrecy and behind closed doors.

One thing is clear: Their work is far from finished, and it's going to stretch well into the new year.

And the little that has happened in public view offers significant clues about what's happening out of public view.

Most notably, the federal grand jury in Washington that has already indicted two key Trump associates is continuing to meet and hear more evidence from prosecutors. The grand jurors' identities are unknown, but their faces are recognizable to the reporters and producers who have been standing inside the courthouse each week. Just a week ago, one of Mueller’s top prosecutors, Jeannie Rhee, was spotted at the courthouse by ABC News.

Mueller became special counsel seven months ago, and he began using the grand jury in Washington shortly thereafter. Such grand juries often last for up to 18 months, and they can be extended for six months at a time.

According to the plea agreement filed with prosecutors four weeks ago, Flynn has agreed to "cooperate fully" with Mueller’s investigation -– and that cooperation could include "answering questions; providing sworn written statements; taking government-administered polygraph examination(s); and participating in covert law enforcement activities."

Flynn also agreed to testify "fully, completely, and truthfully" before any grand juries or trials, and to "promptly" turn over "any and all evidence of crimes" that he knows about, according to the agreement.

Flynn's next court appearance isn’t scheduled for another month, when federal authorities are expected to lay out how helpful he has been to them so far.

Another Trump associate, former campaign adviser George Papadopoulos, has also pleaded guilty to lying to the FBI about his own contacts with Russians, and he has been working with Mueller's team for months.

In Trump's interview with The New York Times, the president said he thinks Mueller is "going to be fair" to him.

A spokesman for Mueller declined to comment for this article.