The chairman of the House Intelligence Committee was on his way to an event in Washington, DC, last Wednesday when the plans abruptly changed.
After taking a brief phone call, Congressman Devin Nunes, a Republican of California, swapped cars and slipped away from his staff, congressional officials said.
He appears to have used that unaccounted-for stretch of time to review classified intelligence files brought to his attention by sources he has said he will not name.
The next morning, Nunes stepped up to a set of microphones in the Capitol complex to declare that he had learned that US spy agencies had "incidentally collected information about US citizens involved in the Trump transition."
Within hours President Donald Trump declared that he had been vindicated for his tweets alleging that Trump Tower had been wiretapped by his predecessor, Barack Obama.
Public attention on the revelation that the FBI was investigating possible coordination between the Trump campaign and Moscow had shifted to questions about whether Trump officials were victims of spying abuse.
And by week's end, a congressional probe capable of threatening Trump was consumed in partisan fighting and scheduling turmoil.
That sequence was largely engineered by a conservative lawmaker from California's Central Valley who has emerged as one of Trump's most tenacious allies on Capitol Hill.
Nunes, 43, has said he is committed to leading an impartial inquiry into Russia's interference in the 2016 US election, and search for any evidence of coordination with Trump or his associates.
But Nunes, who served as an adviser on Trump's transition team, has also at times used his position as chair of the intelligence committee in ways that seem aligned with the interests of the White House.
The committee's course so far has raised concerns about whether it can serve the mission it was given when it was created in the 1970s, putting critical matters of national security above partisan politics.
Former Republican congressman Mike Rogers, who was Nunes' predecessor as chairman, said that both sides have struggled so far to live up to that historic mandate.
"It sows distrust, it shows they don't have a good working foundation for really hard things," Rogers said. "Everybody wants to find what they want to find to affirm their political position. That's no way to run an investigation."
Rep. Devin Nunes's latest stunt could make Trump's Russia problem worse https://t.co/MB6a75UH6p— Vox (@voxdotcom) March 26, 2017
Last year, Nunes repeatedly skirmished with intelligence leaders over assessments that Russia sought to help Trump win.
He has sought to help the White House knock down news stories alleging close ties between Trump associates and the Kremlin.
And Nunes has pushed his panel to focus on lines of inquiry - including hunting the sources of damaging news leaks - that seem more favourable to Trump.
Nunes' latest move came on Saturday, when he made a flurry of announcements that on the surface signalled promising new investigative paths, including an agreement to hear testimony from Trump's former campaign chairman, Paul Manafort.
But to Democrats, Nunes's actions again seemed to show the hidden agenda of the White House.
Most immediately, Nunes cancelled an open hearing that had been scheduled for this Wednesday with former senior officials who have battled Trump.
Among them is former acting Attorney-General Sally Yates, who was fired by Trump; former director of National Intelligence James Clapper, who publicly disputed Trump's wiretapping claim; and former CIA director John Brennan, who has said that Trump should "be ashamed of himself" over his behaviour towards US spy agencies.
When Nunes announced the hearing, it appeared that Republicans would use the session to confront the former Obama Administration officials over a raft of news leaks. But after the five-hour performance by FBI Director James Comey before the committee last week - widely perceived as politically damaging to Trump - GOP members were worried about giving Democrats another open hearing to hammer away on Russian interference in the election and any Trump campaign ties to Moscow.
Trey Gowdy BERATES CNN anchor for even suggesting Nunes did anything wrong - The Right Scoop https://t.co/Gk5i2FgT2C— StrongWomenLoveTrump (@mcgilh) March 26, 2017
Congressman Adam Schiff, of California, the ranking Democrat on the intelligence committee, said that he suspected the cancellation was driven by "very strong pushback from the White House".
Schiff also implied he suspects a White House hand in what he called Nunes' "dead-of-night excursion" to view classified documents. Several congressional officials said they were told about the phone call and swapped cars by members of Nunes' staff.
Jack Langer, a spokesman for Nunes, disputed the depiction. "That account is inaccurate," Langer said. He declined to elaborate.
To review classified files without breaking the law, Nunes would have needed to do so at a secure facility. Congressional officials said that the director of National Intelligence, the FBI and National Security Agency had all indicated that they got no late-night visit from Nunes, a trip that probably would have been entered in security logs.
Nunes has repeatedly refused to say where he went or whether the documents were provided by the White House, including when confronted by committee members during a closed-door meeting on Friday, officials said.
White House spokesman Sean Spicer also refused to rule out a White House role in providing access to the files. "I don't know where he got the documents from, so I can't say anything more than 'I don't know,' " Spicer said during Saturday's White House briefing.
There are clues that such a transaction was coming. Trump said in a recent interview on Fox News that he would "be submitting things before the committee very soon". And Nunes used his opening statement in the Comey hearing to issue a peculiar request for anonymous sources to bring the committee relevant information.
Nunes and Trump could hardly have come from more disparate backgrounds.
Nunes grew up among farmers in the flat stretch of fertile land between Fresno and Bakersfield, California. He has said that he began buying cattle as a teenager and earned an agriculture degree from Cal Poly San Luis Obispo.
But he showed early ambition and aptitude for politics. After serving on the board of trustees for the community college he had attended, Nunes was elected to the House in 2002. He became a protege of former House Speaker John Boehner, who tapped Nunes as chairman of the intelligence panel in 2014.
On Capitol Hill, Nunes is known more for his skills as a political operator than his expertise on policy. He can be intemperate and is a fierce protector of allies.
"He is loyal to his friends. And if they're in a fight, he's going to be on your side in the fight," said Republican Congressman Tom Cole of Oklahoma.
That instinct was on display last week when Nunes withheld information about the intelligence reports he had seen from his own committee while rushing to share the information with the White House. The move outraged Democrats and was seen even by some GOP members as a tactical mistake. Nunes apologised the next day.
"Loyalty can sometimes make you, you know, go a step too far," Cole said. "I'm pretty heartened that [Nunes] recognised that within 24 hours and moved to change it."
Before the Russia issue, Nunes was mainly known in intelligence circles for his role as an architect of the GOP's politically charged investigation of terrorist attacks on US facilities in Benghazi, Libya.
Nunes became an early supporter of Trump and was particularly influential in shaping his national security team. Nunes urged Trump to install retired US Marine General Jim Mattis as Defence Secretary. For CIA chief, Trump turned to a close Nunes ally from the House committee, Republican congressman Mike Pompeo of Kansas.
Nunes has been at odds with Trump in a few cases, most notably when Nunes said that Trump was simply "wrong" about the claim that Obama had ordered a wiretap of Trump Tower to listen to the Republican presidential candidate. But those differences have been rare and seem not to have jeopardised Nunes's standing with the president.
Unlike Trump, Nunes is a consistent critic of Russia and Putin. But the chairman has argued with intelligence agencies about their conclusion that Russia's assault on the presidential campaign - which involved the release of tens of thousands of emails from Democratic Party computer networks - was designed at least in part to help Trump win.
In December, when the Washington Post reported that the CIA had reached that conclusion, Nunes dismissed the finding, saying it was based on "a lot of innuendo, lots of circumstantial evidence, that's it".
Nunes went on to suggest that the FBI didn't agree with the CIA and sought to stage a showdown before the committee. When intelligence officials declined to appear - noting that they were still finishing a final report on the matter - Nunes issued a news release blasting spy agencies for withholding information from Congress. "We want to clarify press reports that the CIA has a new assessment that it has not shared with us," Nunes said.
The move angered then-CIA Director Brennan, who placed a series of calls to Nunes to remind the chairman that he had been briefed on the latest Russia intelligence. Former officials familiar with the matter said that Nunes did not take Brennan's calls for nearly two days, speaking to the CIA director only after Nunes had issued his news release.
Brennan went public himself on December 16, saying that the FBI, DNI and CIA were all in agreement on the Russia hacking and its aims. "There is strong consensus among us on the scope, nature and intent of Russian interference," Brennan said in a public statement.
Langer, Nunes' spokesman, said at the weekend, "every element of that account is false".
When Brennan's staff sought to arrange a call, Nunes "could not participate in the call immediately because he needed to be in a location where he could access a secure line. The call was then arranged for the following morning," Langer said.