He hovers over Washington's seething political swamp like The Phantom.
No one ever sees Robert Mueller, the special counsel leading the Russia collusion investigation; he never speaks.
But he's constantly present, showing his hand through a trickle of court filings, each one stoking speculation through the halls of government, in offices and barrooms, and over dinner tables: What does he have on Donald Trump?
Eighteen months into his investigation, Mueller has the US capital spellbound.
He threw tantalising new bait to Russia-gate adepts late Tuesday when he recommended to a court that Trump's former national security advisor Michael Flynn, who had lied to investigators about his own Russia contacts, be let off without any jail time.
While Flynn was guilty of a "serious" offense, Mueller said in a court filing, he had fully cooperated with investigators in multiple cases, and submitted to interviews 19 times.
What Flynn told them, though, Mueller wasn't saying.
It all adds to a mystique about the veteran prosecutor, who is depicted in fan memes as a Star Wars Jedi or a character from Game of Thrones.
"Mueller is coming," they warn ominously.
WARRIOR AGAINST JUSTICE
Liberals see Mueller as a warrior against injustice, and are whipped up by every court document containing a titbit that potentially links the president to a crime.
Republicans are afraid to even imagine what damage their party faces from the outcome of the probe.
Trump, meanwhile, seems more on edge with each new court filing, blasting out tweets calling the probe an "illegal witch hunt."
It's an extreme makeover for the 74-year-old former Marine, who was a public prosecutor battling the mafia and Russian spies before taking the lead of the Federal Bureau of Investigation just one week in advance of the devastating September 11, 2001 terror attacks.
Director of the FBI for 12 years, he was a very public figure, respected but hardly beloved. Now, he is the invisible star of Washington.
Yet he is barely known by the people that cheer and fear him.
Gaunt and stately, he has only been spotted in public a handful of times this year, reported and heavily forwarded on social media: alone, with no security, crossing a Washington street; dining in a low-key restaurant; getting help at the Georgetown Apple store with his wife of 52 years, Anne Standish.
"Even special counsel needs occasional IT support," tweeted communications consultant Meghan Pianta, who snapped a photo of the couple with one of the Apple techies.
In July, he was also spied in Washington National Airport waiting for a flight, unwittingly just feet away from Donald Trump Jr., the president's son who is believed to be a target of the investigation.
Mueller lives in a gated community in Northern Virginia, and arrives at and leaves work at a non-descript office building in southwest Washington unseen through the parking garage.
He doesn't visit the White House to talk with Trump's lawyers; they go to him. Mostly, his two dozen seasoned investigators and prosecutors do the public work, making court appearances and filings, and likewise letting documents speak for them.
Few know what Mueller is like in person.
Is he the brusque taskmaster who demanded results in the 9/11 investigation barely 24 hours after it took place? Or the quiet, patient but determined chess-player that the Russia collusion investigation's steady march suggests?
News-wise, in notoriously leaky Washington, his shop is hermetically sealed, making it an object of both wonder and disbelief.
He has a spokesman, Peter Carr, who will explain things that are already public record. For any seeking a hint of what is coming up, the answer is always "We decline to comment."
However, by never defending themselves in public, his operation stays vulnerable to attacks like Trump's, who repeatedly has threatened to shut the investigation down.
Mueller, the president said on Twitter on Monday, "is a much different man than people think."
"His out of control band of Angry Democrats, don't want the truth, they only want lies."
Despite hours spent speculating every day by an army of TV analysts, no one knows exactly where the investigation stands.
That could change on Friday when Mueller's team is expected to divulge more of what they have uncovered in a court filing in the case of Trump's former personal lawyer Michael Cohen, who like Flynn has been cooperating.
If he sticks to practice, Mueller still will not give away the whole picture, until he is ready.
His fans, though, are showing signs of impatience.
To wit, Saturday Night Live closed its show last week demanding results in an abridged chorus of the Mariah Carey holiday rocker: "Mueller, All I want For Christmas is You."