In January, after a long day at his London office, Christopher Steele, the former spy turned private investigator, was stepping off a commuter train in Farnham, where he lives, when one of his two phones rang. He'd been looking forward to dinner at home with his wife, and perhaps a glass of wine. It had been their dream to live in Farnham, a town in Surrey with a beautiful Georgian high street, where they could afford a house big enough to accommodate their four children, on nearly an acre of land. Steele, who is fifty-three, looked much like the other businessmen heading home, except for the fact that he kept his phones in a Faraday bag - a pouch, of military-tested double-grade fabric, designed to block signal detection.

A friend in Washington, D.C., was calling with bad news: two Republican senators, Lindsey Graham and Charles Grassley, had just referred Steele's name to the Department of Justice, for a possible criminal investigation. They were accusing Steele - the author of a secret dossier that helped trigger the current federal investigation into President Donald Trump's possible ties to Russia - of having lied to the very F.B.I. officers he'd alerted about his findings. The details of the criminal referral were classified, so Steele could not know the nature of the allegations, let alone rebut them, but they had something to do with his having misled the Bureau about contacts that he'd had with the press. For nearly thirty years, Steele had worked as a close ally of the United States, and he couldn't imagine why anyone would believe that he had been deceptive. But lying to an F.B.I. officer is a felony, an offense that can be punished by up to five years in prison.

The accusations would only increase doubts about Steele's reputation that had clung to him since BuzzFeed published the dossier, in January, 2017. The dossier painted a damning picture of collusion between Trump and Russia, suggesting that his campaign had "accepted a regular flow of intelligence from the Kremlin, including on his Democratic and other political rivals." It also alleged that Russian officials had been "cultivating" Trump as an asset for five years, and had obtained leverage over him, in part by recording videos of him while he engaged in compromising sexual acts, including consorting with Moscow prostitutes who, at his request, urinated on a bed.

In the spring of 2016, Orbis Business Intelligence - a small investigative-research firm that Steele and a partner had founded, in 2009, after leaving M.I.6, Britain's Secret Intelligence Service - had agreed to do opposition research on Trump's murky relationship with Russia. Under the arrangement, Orbis was a subcontractor working for Fusion GPS, a private research firm in Washington. Fusion, in turn, had been contracted by a law firm, Perkins Coie, which represented both Hillary Clinton's Presidential campaign and the Democratic National Committee. Several months after Steele signed the deal, he learned that, through this chain, his research was being jointly subsidized by the Clinton campaign and the D.N.C. In all, Steele was paid a hundred and sixty-eight thousand dollars for his work.

Steele had spent more than twenty years in M.I.6, most of it focussing on Russia. For three years, in the nineties, he spied in Moscow under diplomatic cover. Between 2006 and 2009, he ran the service's Russia desk, at its headquarters, in London. He was fluent in Russian, and widely considered to be an expert on the country. He'd also advised on nation-building in Iraq. As a British citizen, however, he was not especially knowledgeable about American politics. Peter Fritsch, a co-founder at Fusion who has worked closely with Steele, said of him, "He's a career public-service officer, and in England civil servants haven't been drawn into politics in quite the same way they have here. He's a little naïve about the public square."

And so Steele, on that January night, was stunned to learn that U.S. politicians were calling him a criminal. He told Christopher Burrows, with whom he co-founded Orbis, that the sensation was "a feeling like vertigo." Burrows, in his first public interview on the dossier controversy, recalled Steele telling him, "You have this thudding headache - you can't think straight, you have no appetite, you feel ill." Steele compared it to the disorientation that he had felt in 2009, when his first wife, Laura, had died, after a long illness, leaving him to care for their three young children.

That night, Burrows said, Steele and his second wife, Katherine, who have been married since 2012, sat in their living room, wondering what would become of them. Would they be financially ruined by legal costs? (In addition to the criminal referral in the U.S., a Russian businessman, Aleksej Gubarev, had filed a libel lawsuit against Steele, saying that the dossier had falsely accused his company of helping the Russian government hack into the Democratic Party's internal e-mail system.) Would Steele end up in a U.S. federal penitentiary? Would a Putin emissary knife him in a dark alley somewhere?

In conversations with friends, Steele said he hoped that in five years he'd look back and laugh at the whole experience. But he tended toward pessimism. No matter how the drama turned out, "I will take this to my grave," he often predicted. A longtime friend of Steele's pointed out to me that Steele was in a singularly unenviable predicament. The dossier had infuriated both Vladimir Putin and Donald Trump by divulging allegedly corrupt dealings between them. "You've got oligarchs running both superpowers," the friend said. "And, incredibly, they both hate this same guy."

Legal experts soon assured Steele that the criminal referral was merely a political stunt. Nevertheless, it marked a tense new phase in the investigation into Trump's alleged ties to Russia. The initial bipartisan support in Congress for a serious inquiry into foreign meddling in America's democracy had given way to a partisan brawl. Trump's defenders argued that Steele was not a whistle-blower but a villain - a dishonest Clinton apparatchik who had collaborated with American intelligence and law-enforcement officials to fabricate false charges against Trump and his associates, in a dastardly attempt to nullify the 2016 election. According to this story line, it was not the President who needed to be investigated but the investigators themselves, starting with Steele. "They're trying to take down the whole intelligence community!" Steele exclaimed one day to friends. "And they're using me as the battering ram to do it."

It was not the first time that a congressional investigation had been used as a tool for destroying someone's reputation. Whenever a scandal hit Washington, opponents used subpoenas, classified evidence, and theatrical public hearings to spread innuendo, confusion, and lies. Senators Grassley and Graham declined to be interviewed for this article, but in January Grassley, the chairman of the Senate Judiciary Committee, gave a speech on the Senate floor defending the criminal referral. He noted that Steele had drawn on Russian contacts to amass the dossier. "Who was actually colluding with Russians?" Grassley asked. "It's becoming more clear."

Democratic members of the committee, who had not been consulted by Republicans about the criminal referral against Steele, were enraged. The California senator Dianne Feinstein, the ranking minority member on the committee, declared that the Republicans' goals were "undermining the F.B.I. and Special Counsel Mueller's investigation" and "deflecting attention" from it. Feinstein said that the criminal referral provided no evidence that Steele had lied, and, she added, "not a single revelation in the Steele dossier has been refuted."

Sheldon Whitehouse, a Democratic senator from Rhode Island, is a former prosecutor who also serves on the Judiciary Committee. "To impeach Steele's dossier is to impeach Mueller's investigation," he told me. "It's to recast the focus back on Hillary." The Republicans' aim, he believed, was to "create a false narrative saying this is all a political witch hunt."

Indeed, on January 18th, the staff of Devin Nunes, the Republican chairman of the House Intelligence Committee, produced a report purporting to show that the real conspiracy revolved around Hillary Clinton. "The truth," Nunes said, is that Clinton "colluded with the Russians to get dirt on Trump, to feed it to the F.B.I. to open up an investigation into the other campaign." Glenn Kessler, who writes the nonpartisan Fact Checker blog at the Washington Post, awarded Nunes's statement four Pinocchios - his rating for an outright lie. "There is no evidence that Clinton was involved in Steele's reports or worked with Russian entities to feed information to Steele," Kessler wrote.

Nonetheless, conservative talk-show hosts amplified Nunes's message. On Fox News, Tucker Carlson denounced Steele as "an intense partisan with passionately left-wing views about American politics," and said, inaccurately, that his "sloppy and reckless" research "appears to form the basis" of the entire Mueller investigation. Sean Hannity charged that Steele's dossier was "claptrap" filled with "Russian lies" that were intended to poison "our own intelligence and law-enforcement network" against Trump. The editorial page of the Wall Street Journal accused Steele of turning the F.B.I. into "a tool of anti-Trump political actors." Rush Limbaugh warned his radio listeners, "The battle is between people like us and the Deep State who are trying to keep hidden what they did."

President Trump had mocked "the dirty dossier," suggesting that a "failed spy" had relied on "made-up facts by sleazebag political operatives." But on February 8th the President denounced Steele by name for the first time. "Steele of fraudulent Dossier fame," he tweeted, was "all tied into Crooked Hillary."

Two days later, Burrows, of Orbis, was at his home, in Winchester, southwest of London, struggling to express to me how odd and disturbing it was to have his business partner targeted by the President of the United States. A tight-lipped fifty-nine-year-old who is conservative in politics and in manner, Burrows, like Steele, had spent decades as a British intelligence officer. "This whole thing has been quite surreal," he said. "We are being made into a political football, in U.S. terms, which we really regret. Chris is being accused of being the heart of some Deep State conspiracy, and he's not even in your state."

Steele's lawyers have advised him not to speak publicly about the controversy, and, because he is a former intelligence officer, much of his life must remain secret. His accusers know this, and, as Senator Whitehouse explained, "they are using selective declassification as a tactic - they use declassified information to tell their side, and then the rebuttal is classified." Both the criminal referral and Nunes's report used secret evidence to malign Steele while providing no means for his defenders to respond without breaching national-security secrets. But interviews with Steele's friends, colleagues, and business associates tell a very different story about how a British citizen became enmeshed in one of America's most consequential political battles.

Steele was born in 1964 in Aden, then the capital of Yemen. His father worked for the U.K.'s national weather service, and had postings overseas and in Great Britain. Steele's family was middle class, but its roots were blue-collar: one of Steele's grandfathers was a Welsh coal miner. An outstanding student, Steele was accepted at Cambridge University in 1982. He soon set his sights on becoming the president of the Cambridge Union, the prestigious debating society. It is such a common path for ambitious future leaders that, according to one former member, its motto should be "The Egos Have Landed." Getting elected president requires shrewd political skills, and Steele secured the position, in part, by muscling the university newspaper, for which he had been writing, into endorsing his candidacy. His jockeying created enemies. One anonymous rival recently told the Daily Mail that Steele used to be a "little creep."

Steele was a middle-of-the-road Labour Party supporter, and at the Cambridge Union his allies, known as the Anti-Establishment Faction, were state-schooled, middle-class students. Steele's camp competed against a blue-blooded Establishment Faction and a right-wing Libertarian Faction. His longtime friend, who was part of a like-minded society at Oxford, said, "Almost all of us had come from less posh families, and suffered a bit from the impostor syndrome that made us doubt we belonged there, so we worked many times harder to prove ourselves." He recalled Steele as an "astoundingly diligent" student with "huge integrity," adding, "He just puts the bit in his teeth and charges the hill. He's almost like a cyborg."

Graham Davies, now a well-known public-speaking coach in the U.K., became friends with Steele in the Cambridge Union. He described him as "ultra low-key but ultra high-intensity," adding, "He's a very quiet guy who listens more than he talks, which made him stand out." Davies went on, "Most of us like a bit of the spotlight, but Chris has always been the opposite. That's been part of his integrity. He's quietly in control." Davies, who is a conservative, told me that Steele has many conservative friends. (Steele supported the Labour government of Tony Blair until the Iraq War, but he voted for a local Conservative official in his home county.) "He's not an ideologue," Davies said. "He's got his political views, but he's a pragmatic thinker. Fairness, integrity, and truth, for him, trump any ideology."

Steele is said to be the first president of the Cambridge Union to invite a member of the Palestine Liberation Organization to speak. And he presided over numerous high-profile political debates, including one in which the proposition that President Ronald Reagan's foreign policies had hurt the U.K. carried the house.

Tellingly, none of Steele's old friends seem to remember the first time they met him. Of average height and build, with pleasant features, a clean-cut style of dress, and a cool, neutral gaze, he didn't draw attention to himself. He was a natural candidate to become professionally unnoticeable. Davies, who dines several times a year with Steele and other schoolmates, said, "He's more low-key than Smiley" - the John le Carré character. But, he noted, whenever Steele took on a task "he was like a terrier with a bone - when something needs investigating, he applies the most intense intellect I've ever seen."

Steele graduated in 1986, with a degree in social and political science, and initially thought that he might go into journalism or the law. One day, though, he answered a newspaper ad seeking people interested in working abroad. The advertiser turned out to be M.I.6, which, after a battery of tests, recruited Steele into its Russian-language program. By the time he was in his mid-twenties he was living in Moscow.

Steele worked out of the British Embassy for M.I.6, under diplomatic cover. His years in Moscow, 1990 to 1993, were among the most dramatic in Russian history, a period that included the collapse of the Communist Party; nationalist uprisings in Ukraine, the Caucasus, and the Baltic states; and the dissolution of the Soviet Union. Boris Yeltsin gained ultimate power in Russia, and a moment of democratic promise faded as the K.G.B. - now called the F.S.B. - reasserted its influence, oligarchs snapped up state assets, and nationalist political forces began to emerge. Vladimir Putin, a K.G.B. operative returning from East Germany, reinvented himself in the shadowy world of St. Petersburg politics. By the time Steele left the country, optimism was souring, and a politics of resentment - against the oligarchs, against an increasing gap between rich and poor, and against the West - was taking hold.

After leaving Moscow, Steele was assigned an undercover posting with the British Embassy in Paris, but he and a hundred and sixteen other British spies had their cover blown by an anonymously published list. Steele came in from the cold and returned to London, and in 2006 he began running its Russia desk, growing increasingly pessimistic about the direction of the Russian Federation.

Steele's already dim view of the Kremlin darkened in November, 2006, when Alexander Litvinenko, a former Russian K.G.B. officer and a Putin critic who had been recruited by M.I.6, suffered an agonizing death in a London hospital, after drinking a cup of tea poisoned with radioactive polonium-210. Moscow had evidently sanctioned a brazen murder in his own country. Steele was put in charge of M.I.6's investigation. Authorities initially planned to indict one suspect in the murder, but Steele's investigative work persuaded them to indict a second suspect as well. Nine years later, the U.K.'s official inquiry report was finally released, and it confirmed Steele's view: the murder was an operation by the F.S.B., and it was "probably approved" by Vladimir Putin.

Steele has never commented on the case, or on any other aspect of his intelligence work, but Richard Dearlove, who led M.I.6 from 1999 to 2004, has described his reputation as "superb." A former senior officer recalls him as "a Russia-area expert whose knowledge I and others respected - he was very careful, and very savvy." Another former M.I.6 officer described him as having a "Marmite" personality - a reference to the salty British spread, which people either love or hate. He suggested that Steele didn't appear to be "going places in the service," noting that, after the Cold War, Russia had become a backwater at M.I.6. But he acknowledged that Steele "knew Russia well," and that running the Russia desk was "a proper job that you don't give to an idiot."

The British Secret Intelligence Service is highly regarded by the United States, particularly for its ability to harvest information from face-to-face sources, rather than from signals intelligence, such as electronic surveillance, as the U.S. often does. British and American intelligence services work closely together, and, while Steele was at M.I.6, British intelligence was often included in the U.S. President's daily-briefing reports. In 2008, Michael Hayden, the C.I.A. director, visited the U.K., and Steele briefed him on Russian developments. The following year, President Obama visited the U.K., and was briefed on a report that Steele had written about Russia. Steve Hall, a former chief of the C.I.A.'s Central Eurasia Division, which includes Russia, the former Soviet states, and the Balkans, told me, "M.I.6 is second only perhaps to the U.S. in its ability to collect intelligence from Russia." He added, "We've always coordinated closely with them because they did such a great job. We're playing in the Yankee Stadium of espionage here. This isn't Guatemala."

In 2008, Steele informed M.I.6 that he planned to leave the service and open a commercial intelligence firm with Burrows. He left in good standing, but his exit was hastened, because M.I.6 regarded his plans as a potential conflict of interest. Launching the business was a risky move: London was filled with companies run by former intelligence officers selling their contacts and inside knowledge. To differentiate itself, Orbis, which opened its office in Mayfair, attempted to exploit Steele's Russian expertise. The strategy appears to have paid off. According to people with knowledge of the company, Orbis grossed approximately twenty million dollars in its first nine years. Steele now drives a Land Rover Discovery Sport, and belongs to a golf club. He also runs a bit, but the feats that kept him in shape while he was a spy - he ran six marathons and twenty-five half-marathons, and competed in a dozen Olympic-length triathlon events - have been replaced by the carrying of a briefcase. His free time is devoted largely to his family, which includes three cats, one of whom not long ago replicated the most infamous allegation in the Steele dossier by peeing on a family member's bed.

Orbis's clients are mostly businesses or law firms representing corporations. Burrows said that although the company has fewer than ten full-time employees, "we're a bit like the bridge on the Starship Enterprise - we're a small group but we manage an enormous ship." To serve its clients, Orbis employs dozens of confidential "collectors" around the world, whom it pays as contract associates. Some of the collectors are private investigators at smaller firms; others are investigative reporters or highly placed experts in strategically useful jobs. Depending on the task and the length of engagement, the fee for collectors can be as much as two thousand dollars a day. The collectors harvest intelligence from a much larger network of unpaid sources, some of whom don't even realize they are being treated as informants. These sources occasionally receive favors - such as help in getting their children into Western schools - but money doesn't change hands, because it could risk violating laws against, say, bribing government officials or insider trading. Paying sources might also encourage them to embellish.

Steele has not been to Russia, or visited any former Soviet states, since 2009. Unlike some of his former M.I.6 colleagues, he has not been declared persona non grata by Putin's regime, but, in 2012, an Orbis informant quoted an F.S.B. agent describing him as "an enemy of Mother Russia." Steele concluded that it would be difficult for him to work in the country unnoticed. The firm guards the identities of its sources, but it's clear that many Russian contacts can be interviewed elsewhere, and London is the center of the post-Soviet Russian diaspora.

Orbis often performs anti-corruption investigations for clients attempting internal reviews, and helps hedge funds and other financial companies perform due diligence or obtain strategic information. One Orbis client who agreed to talk to me, a Western businessman with interests in Russia and Ukraine, described Steele to me as "very efficient, very professional, and very credible." He said that his company had successfully cross-checked Steele's research with other people, adding, "I don't know anyone who's been critical of his work. His reports are very good. It's an absolute no-brainer that he's just a political target. They're trying to shoot the messenger."

Orbis promises confidentiality, and releases no information on its clientele. Some of its purported clients, such as a major Western oil company, are conventional corporations. Others are controversial, including a London law firm representing the interests of Oleg Deripaska, the billionaire victor of Russia's aluminum wars, a notoriously violent battle. He has been described as Putin's favorite oligarch. Steele's possible financial ties to Deripaska recently prompted Senator Grassley to demand more information from the London law firm. If a financial trail between Deripaska and Orbis can be established, it is likely to raise even more questions about Steele, because Deripaska has already figured in the Russia investigation, in an unsavory light. Paul Manafort, Trump's former campaign manager, has been accused of defrauding Deripaska's company while working for it in Ukraine. (Manafort has been indicted by Special Counsel Robert Mueller on charges of money laundering and other financial crimes. He has pleaded not guilty.) Even if Steele's rumored work for Deripaska is aboveboard, it illustrates the transition that he has made from the world of government service to the ethically gray world of commerce. Oligarchs battling other oligarchs provide some of the most lucrative work for investigators with expertise in Russia. Orbis maintains that, as long as its activities are limited to providing litigation support for Western law firms acting in Western courts, it is helping to settle disputes in a more civilized way than they would be in Russia. But Steele stepped into a murkier realm when he left M.I.6.

Republican claims to the contrary, Steele's interest in Trump did not spring from his work for the Clinton campaign. He ran across Trump's name almost as soon as he went into private business, many years before the 2016 election. Two of his earliest cases at Orbis involved investigating international crime rings whose leaders, coincidentally, were based in New York's Trump Tower.

Steele's first client after leaving M.I.6 was England's Football Association, which hoped to host the World Cup in 2018, but suspected dirty dealings by the governing body, fifa. England lost out in its bid to Russia, and Steele determined that the Kremlin had rigged the process with bribes. According to Ken Bensinger's "Red Card," an upcoming book about the scandal, "one of Steele's best sources" informed him that the Deputy Prime Minister, Igor Sechin - now the C.E.O. of the Russian state-controlled oil giant Rosneft - is suspected of having travelled to Qatar "to swap World Cup votes."

Steele appears to have spoken anonymously to the Sunday Times of London about the case. An "ex-M.I.6 source" who investigated the bidding process told the paper, "The key thing with Russia was six months before the bid, it got to the point where the country feared the humiliation of being beaten and had to do something ... Putin dragged in all sorts of capabilities." He added, "Don't expect me or anyone else to produce a document with Putin's signature saying 'Please, X, bribe Y with this amount in this way.' He's not going to do that."

Steele might have been expected to move on once his investigation of the bidding was concluded. But he had discovered that the corruption at fifa was global, and he felt that it should be addressed. The only organization that could handle an investigation of such scope, he felt, was the F.B.I. In 2011, Steele contacted an American agent he'd met who headed the Bureau's division for serious crimes in Eurasia. Steele introduced him to his sources, who proved essential to the ensuing investigation. In 2015, the Justice Department indicted fourteen people in connection with a hundred and fifty million dollars in bribes and kickbacks. One of them was Chuck Blazer, a top fifa official who had embezzled a fortune from the organization and became an informant for the F.B.I. Blazer had an eighteen-thousand-dollar-per-month apartment in Trump Tower, a few floors down from Trump's residence.

Nobody had alleged that Trump knew of any fifa crimes, but Steele soon came across Trump Tower again. Several years ago, the F.B.I. hired Steele to help crack an international gambling and money-laundering ring purportedly run by a suspected Russian organized-crime figure named Alimzhan Tokhtakhounov. The syndicate was based in an apartment in Trump Tower. Eventually, federal officials indicted more than thirty co-conspirators for financial crimes. Tokhtakhounov, though, eluded arrest, becoming a fugitive. Interpol issued a "red notice" calling for his arrest. But, in the fall of 2013, he showed up at the Miss Universe contest in Moscow - and sat near the pageant's owner, Donald Trump.

"It was as if all criminal roads led to Trump Tower," Steele told friends.

Burrows told me that he and Steele made a pact when they left M.I.6: "We both agreed it was a duty to alert U.K. and allied authorities if we came across anything with national-security dimensions. It comes from a very long government service. We still have that ethos of wanting to do the right thing by our authorities."

By working with law-enforcement authorities on investigations, Steele has kept a foot in his former life. Some critics have questioned the propriety of this. Lindsey Graham recently argued, in the Washington Post, "You can be an F.B.I. informant. You can be a political operative. But you can't be both, particularly at the same time."

Burrows said that on several occasions Orbis had warned authorities about major security threats. Three years ago, a trusted Middle Eastern source told Orbis that a group of isis militants were using the flow of refugees from Syria to infiltrate Europe. Orbis shared the information with associates who relayed the intelligence to German security officials. Several months later, when a concert hall in Paris, the Bataclan, was attacked by terrorists, Burrows and Steele felt remorse at not having notified French authorities as well. When Steele took his suspicions about Trump to the F.B.I. in the summer of 2016, it was in keeping with Orbis protocol, rather than a politically driven aberration.

Even before Steele became involved in the U.S. Presidential campaign, he was convinced that the Kremlin was interfering in Western elections. In April of 2016, not long before he took on the Fusion assignment, he finished a secret investigation, which he called Project Charlemagne, for a private client. It involved a survey of Russian interference in the politics of four members of the European Union - France, Italy, the United Kingdom, and Germany - along with Turkey, a candidate for membership. The report chronicles persistent, aggressive political interference by the Kremlin: social-media warfare aimed at inflaming fear and prejudice, and "opaque financial support" given to favored politicians in the form of bank loans, gifts, and other kinds of support. The report discusses the Kremlin's entanglement with the former Italian Prime Minister Silvio Berlusconi and the French right-wing leader Marine Le Pen. (Le Pen and Berlusconi deny having had such ties.) It also suggests that Russian aid was likely given to lesser-known right-wing nationalists in the United Kingdom and elsewhere. The Kremlin's long-term aim, the report concludes, was to boost extremist groups and politicians at the expense of Europe's liberal democracies. The more immediate goal was to "destroy" the E.U., in order to end the punishing economic sanctions that the E.U. and the U.S. had imposed on Russia after its 2014 political and military interference in Ukraine.

Although the report's language was dry, and many of the details familiar to anyone who had been watching Russia closely, Project Charlemagne was the equivalent of a flashing red light. It warned that Russian intelligence services were becoming more strategic and increasingly disruptive. Russian interference in foreign elections, it cautioned, was only "likely to grow in size and reach over time."

In the spring of 2016, Steele got a call from Glenn Simpson, a former investigative reporter for the Wall Street Journal who, in 2011, had left journalism to co-found Fusion GPS. Simpson was hoping that Steele could help Fusion follow some difficult leads on Trump's ties to Russia. Simpson said that he was working for a law firm, but didn't name the ultimate client.

The funding for the project originally came from an organization financed by the New York investor Paul Singer, a Republican who disliked Trump. But, after it became clear that Trump would win the Republican nomination, Singer dropped out. At that point, Fusion persuaded Marc Elias, the general counsel for the Clinton campaign, to subsidize the unfinished research. This bipartisan funding history belies the argument that the research was corrupted by its sponsorship.

Steele and Simpson had previously worked together, and they shared a mutual fascination with Russian oligarchs and international organized crime. They had symbiotic approaches. Fusion focussed on open-source research - mind-numbing dives into the fine print of public records. Steele's specialty was gathering intelligence from informed sources, many of them Russian.

The dossier alleges that Putin backed Donald Trump over Hillary Clinton in order to "sow discord and disunity" in America. Illustration by Cristiana Couceiro; photographs by Alexei Nikolsky / AFP / Getty (man); Melina Mara / The Washington Post / Getty (woman); Frank Lukasseck / Getty (binoculars)

One question particularly gnawed at Simpson. Why had Trump repeatedly gone to Russia in search of business, yet returned empty-handed? Steele was tantalized, and took the job, thinking that he'd find evidence of a few dodgy deals, and not much else. He evidently didn't consider the danger of poking into a Presidential candidate's darkest secrets. "He's just got blinkers," Steele's longtime friend told me. "He doesn't put his head in the oven so much as not see the oven."

Within a few weeks, two or three of Steele's long-standing collectors came back with reports drawn from Orbis's larger network of sources. Steele looked at the material and, according to people familiar with the matter, asked himself, "Oh, my God - what is this?" He called in Burrows, who was normally unflappable. Burrows realized that they had a problem. As Simpson later put it, "We threw out a line in the water, and Moby-Dick came back."

Steele's sources claimed that the F.S.B. could easily blackmail Trump, in part because it had videos of him engaging in "perverted sexual acts" in Russia. The sources said that when Trump had stayed in the Presidential suite of Moscow's Ritz-Carlton hotel, in 2013, he had paid "a number of prostitutes to perform a 'golden showers' (urination) show in front of him," thereby defiling a bed that Barack and Michelle Obama had slept in during a state visit. The allegation was attributed to four sources, but their reports were secondhand - nobody had witnessed the event or tracked down a prostitute, and one spoke generally about "embarrassing material." Two sources were unconnected to the others, but the remaining two could have spoken to each other. In the reports Steele had collected, the names of the sources were omitted, but they were described as "a former top-level Russian intelligence officer still active inside the Kremlin," a "member of the staff at the hotel," a "female staffer at the hotel when Trump had stayed there," and "a close associate of Trump who had organized and managed his recent trips to Moscow."

More significant, in hindsight, than the sexual details were claims that the Kremlin and Trump were politically colluding in the 2016 campaign. The Russians were described as having cultivated Trump and traded favors with him "for at least 5 years." Putin was described as backing Trump in order to "sow discord and disunity both within the U.S." and within the transatlantic alliance. The report claimed that, although Trump had not signed any real-estate-development deals, he and his top associates had repeatedly accepted intelligence from the Kremlin on Hillary Clinton and other political rivals. The allegations were astounding - and improbable. They could constitute treason even if they were only partly true.

According to people familiar with the matter, as Steele began to assemble the first of seventeen memos, which became the dossier, Burrows expressed reservations about including the golden-showers allegation. He had a cautious temperament, and worried about the impact that the sensational item might have. But Steele argued that it would be dishonest and distorting to cherry-pick details, and that the possibility of a potential American President being subject to blackmail was too important to hide. "That's classic Steele," his longtime friend told me. "He's so straight."

In a fateful decision, Steele chose to include everything. People familiar with the matter say that Steele knew he could either shred the incendiary information or carry on. If he kept investigating, and then alerted officials who he thought should know about his findings, he feared that his life - and, indeed, the life of anyone who touched the dossier - would never be the same.

At the time, Steele figured that almost nobody would ever see the raw intelligence. The credibility of Steele's dossier has been much debated, but few realize that it was a compilation of contemporaneous interviews rather than a finished product. Orbis was just a subcontractor, and Steele and Burrows reasoned that Fusion could, if it wished, process the findings into an edited report for the ultimate client. So Orbis left it up to Fusion to make the judgment calls about what to leave in, and to decide whether to add caveats and source notes of the kind that accompany most government intelligence reports.

John Sipher spent twenty-eight years as a clandestine officer in the C.I.A., and ran the agency's Russia program before retiring, in 2014. He said of Steele's memos, "This is source material, not expert opinion." Sipher has described the dossier as "generally credible," although not correct in every detail. He said, "People have misunderstood that it's a collection of dots, not a connecting of the dots. But it provided the first narrative saying what Russia might be up to." Alexander Vershbow, a U.S. Ambassador to Russia under George W. Bush, told me, "In intelligence, you evaluate your sources as best you can, but it's not like journalism, where you try to get more than one source to confirm something. In the intelligence business, you don't pretend you're a hundred per cent accurate. If you're seventy or eighty per cent accurate, that makes you one of the best."