WASHINGTON — Unlike the president, Robert Mueller hasn’t uttered one word in public about his Russia investigation in the year since he was appointed special counsel. And that is rattling just about everyone involved.

What’s he up to? When will he bring the probe to an end?

He doesn’t have to say, and he’s not.

A year into the investigation, the stern-looking prosecutor is everywhere and nowhere at the same time. In that time, the breadth and stealth of investigations surrounding Trump have unsettled the White House and its chief occupant, and have spread to Capitol Hill, K Street, foreign governments and, as late as last week, corporate boardrooms.

With lawmakers eying midterm elections and President Donald Trump publicly mulling whether he will sit for an interview with Mueller, Republican calls are growing for the special counsel to end his investigation. Vice President Mike Pence and others have said it publicly. GOP lawmakers insist they’ve seen no evidence of collusion between Russians and Trump’s 2016 election campaign.

The longer the investigation runs, those calls are likely to amplify.

House Speaker Paul Ryan, who has steadfastly supported the special counsel, seemed to change his tone a bit Thursday.

“I think he should be free to do his job, but I would like to see it get wrapped up, of course,” Ryan said of Mueller. “I mean we want to see this thing come to its conclusion, but again I’ve always said he should be free to finish his job.”

Mueller is investigating Russian interference in the election, whether Trump’s campaign was involved and possible obstruction of justice. And by the standards of previous special counsel investigations, his actually has so far gone fairly quickly. Since he was appointed on May 17, 2017, Mueller’s office has charged 19 people and three Russian companies. He has charged four Trump campaign advisers, including former national security adviser Michael Flynn and ex-Trump campaign chairman Paul Manafort.

The probe has also ensnared countless Washington insiders who have been called to testify or found themselves under scrutiny, including lobbyists and foreign representatives who may have illegally sought to influence the administration.