FBI agents are plumbing hundreds of thousands of emails in search of potentially incriminating evidence against Democratic nominee Hillary Clinton, in a high-pressure probe seven days before the US presidential election.
What will come out of it and when is not known, but the impact of the FBI's bombshell discovery of a new trove of Clinton emails is already reverberating in the neck-and-neck race for the White House.
Trump has seized on the October surprise to put Clinton on the defensive, while Democrats have assailed FBI chief James Comey for breaking with policy and protocol by effectively reopening an investigation into Clinton's handling of state secrets so close to the elections.
"He's dangling out there that they have some information," complained Clinton campaign manager Robby Mook.
"We find out he didn't even have a warrant to know what it was. And he's coming out and saying, well, I have some information, it might be important, it might not. It might be pertinent."
Comey informed Congress on Friday that the FBI had learned of the existence of the emails.
He said they should be reviewed because they could be relevant to an earlier probe into Clinton's use of a private server to send emails while she was secretary of state.
But with the electoral clock ticking, the review has just begun.
It wasn't until Sunday that a judge signed off on an order authorizing the FBI to search through the hundreds of thousands of emails apparently found on a laptop taken from Anthony Weiner, the estranged husband of close Clinton aide Huma Abedin.
Weiner, a disgraced former congressman, was under investigation for allegedly sending a text of a sexual nature to a 15-year-old girl.
According to media reports citing sources close to the investigation, the FBI -- which made a copy of the laptop hard drive -- is targeting only email belonging to Abedin, who apparently had shared the laptop with her husband.
Like her mentor, Abedin used other email accounts besides her state.gov account, including a Yahoo account and clintonemail.com, based out of Clinton's private server, the reports said.
To sort through the mass of information, the FBI uses software to scan for key words in address and subject lines, with Comey regularly briefed on the progress of the search, according to reports.
Under questioning by the FBI in April, Abedin acknowledged that she routinely used private accounts to send emails, regardless of whether they contained secret information, according to excerpts released by the FBI.
Several dozen investigators, including computer experts and counter-intelligence specialists, working out of a building in Washington, spent more than a year on the probe into Clinton's private server.
The latest twist in the saga has overjoyed Trump supporters and dismayed Democrats, with both sides agreeing on just one thing: they want to know more.
The Justice Department has only partially responded to these concerns, sending a letter to lawmakers Monday.
'As expeditiously as possible'
"We assure you that the department will continue to work closely with the FBI and together, dedicate all necessary resources and take appropriate steps as expeditiously as possible," wrote Peter Kadzik, the assistant attorney general.
Attorney General Loretta Lynch spoke with Comey in person about the probe on Monday.
But Democrats have not been reassured, denouncing what they see as serious violations of Justice Department policy not to comment on ongoing investigations and to avoid actions that could influence an election's outcome.
"This is not how federal investigations are conducted," thundered The New York Times, which endorsed Clinton, in an editorial titled "James Comey's Big Mistake."
"In claiming to stand outside politics, Mr Comey has instead created the hottest political football of the 2016 election," it said.
Even if the search turns up classified information, the FBI might wind up reaffirming its finding in July that Clinton did not intentionally put at risk US security.
On the other hand, one can only imagine what would happen if the FBI found something more serious in emails, especially if they turn out to have been among ones Clinton was thought to have erased.
The US Constitution grants the president wide immunity from prosecution related to offenses committed during his or her mandate -- which are the only sort that can theoretically lead to impeachment. It is unclear whether immunity would extend to prior offenses.
But in any case, Republican lawmakers are almost certain to hound Clinton until the elections and beyond, using congressional hearings as a weapon.
Meanwhile, the FBI unexpectedly released documents concerning ex-president Bill Clinton's pardon of the husband of a wealthy Democratic donor, in a document dump quickly criticized by Democrats for its odd timing just a week before Election Day.
But the FBI insisted that the documents into the probe -- which was closed without charges in 2005 -- were simply posted "per the standard procedure" following Freedom of Information Act requests.