“I’ve seen the transcript,” a Republican member of the House Intelligence Committee told me recently. “It was explained to us. I don’t know why Flynn did it.” The congressman was talking about a conversation that took place in late December between Michael Flynn, then Trump’s incoming national-security adviser, and the Russian Ambassador, Sergey Kislyak. He noted that he didn’t know why Flynn had discussed sanctions with Kislyak, and wasn’t sure whether he had crossed any legal or ethical lines.

Flynn’s conversation with Kislyak is now at the center of F.B.I. and congressional investigations into Russian interference in the Presidential election, which are seeking to determine whether there was coördination between Russia and the Trump campaign. Yesterday, the Wall Street Journal reported that Flynn is seeking immunity from the Justice Department and the House and Senate committees in return for his coöperation and testimony. “Gen. Flynn certainly has a story to tell, and he very much wants to tell it, should the circumstances permit,” Flynn’s lawyer, Robert Kelner, said in a statement. (It’s notable that Flynn chose to be represented by Kelner, a self-described #NeverTrump Republican who voted for the independent candidate Evan McMullin.)

I asked the Republican congressman if he believed that Flynn did anything illegal in the phone call, in which Flynn discussed actions taken the same day by the Obama Administration. A rarely enforced eighteenth-century law known as the Logan Act makes it illegal to “influence the measures or conduct of any foreign government” or “defeat the measures of the United States” in disputes with an adversary. “That’s open to question,” the Republican congressman told me.

If a former high-ranking official like Flynn is offered immunity, it generally means he can offer up a bigger fish. “The problem with being high up in government is that there are few people higher for the purposes of targeting,” the legal scholar Jonathan Turley noted today on his blog. “People get immunity to incriminate the Flynns of the world. With the exception of the President himself, it is hard to see who Flynn could offer as a possible target in exchange for his own immunity.”

As a senior White House official recently told me, the early Trump campaign attracted a lot of “marginalia”—officials who were unwelcome in more traditional Republican campaigns. Flynn, who was Trump’s longest-serving foreign-policy adviser, was among them. In August, 2014, after the Obama Administration fired him from running the Defense Intelligence Agency, the Army General grew increasingly hostile to the President and fixated on a dark view of Islam that was percolating on the fringes of the right. “Fear of Muslims is RATIONAL,” Flynn once tweeted.

Flynn first met Trump in August, 2015, just weeks after Trump entered the Presidential race. A few weeks later, Flynn appeared on RT, Russia’s English-language TV network, which the American intelligence community recently described as “the Kremlin’s principal international propaganda outlet.” In December, 2015, Flynn gave a paid speech in Moscow and attended RT’s tenth-anniversary gala, where he dined sitting next to Vladimir Putin. Earlier this month, the Washington Post reported that Flynn “collected nearly $68,000 in fees and expenses from Russia-related entities in 2015,” including some forty-five thousand dollars for the RT event.

By early 2016, Flynn was one of Trump’s most enthusiastic supporters and public surrogates. Trump even considered him as a potential running mate. He became well known during the campaign for his unrestrained attacks on Hillary Clinton. At the Republican Convention last summer, he led G.O.P. delegates in a chant of “lock her up.” During an interview with NBC on September 25th, commenting on aides to Clinton who had received immunity agreements in the F.B.I.’s investigation Clinton’s handling of classified information, he said, “When you are given immunity, that means you have probably committed a crime." At a campaign rally two days later, Trump echoed the remark: “If you’re not guilty of a crime, what do you need immunity for?”

Three of the four Trump campaign advisers whose names have surfaced in connection with the F.B.I. investigation—Paul Manafort, Trump’s former campaign chairman; Roger Stone, a longtime Trump adviser who officially worked on the campaign when it launched, in 2015; and Carter Page, who served as a foreign-policy adviser—never made it to the White House. Flynn was different.

After the election, Trump was slow to assemble a White House team and Cabinet, but one of the first personnel decisions he made was naming Flynn as his national-security adviser, on November 18th. On December 29th, Barack Obama announced that, in retaliation for Russia’s meddling in the election, the U.S. would expel thirty-five Russian diplomats, close down two Russian diplomatic facilities, and impose new economic sanctions. It was one of the most sensitive moments in U.S.-Russia relations in decades, and Kislyak texted Flynn asking if they could talk.

The call, in which the two men discussed the new Obama sanctions, was monitored by American intelligence, and the transcript was circulated within the Obama Administration. On January 13th, the day after details of the call became public, the Trump spokesman Sean Spicer told reporters that the call “never touched on the sanctions.” In preparing Vice-President-elect Mike Pence for TV interviews, Flynn apparently denied that he and Kislyak discussed sanctions, and Pence repeated that assertion on CBS’s “Face the Nation,” on January 15th.

These denials apparently caught the attention of F.B.I. agents, who interviewed Flynn in late January. On January 26th, Sally Yates, the acting Attorney General, who was later fired by Trump, informed the White House that Flynn’s account of what he discussed with the Russian Ambassador was false and made him vulnerable to blackmail by the Russians. Despite the F.B.I. interview and the Justice Department’s warning, Trump took no actions against Flynn. (The White House later said that it conducted a review of the call and determined that there were no legal issues.) On January 28th, Flynn was on the line when Trump and Putin held an hour-long conversation.

On February 8th, Flynn himself insisted to the Washington Post that he and Kislyak did not talk about sanctions, an assertion that the Post reported was false and which Flynn then clarified. With the issue public and creating a firestorm, Trump finally fired Flynn, five days later.

This morning, Trump weighed in on Flynn’s immunity request, an extremely unusual decision considering that the request is before his own Justice Department. “Mike Flynn should ask for immunity in that this is a witch hunt (excuse for big election loss), by media & Dems, of historic proportion!” he posted on Twitter.

Democrats want to know why it took weeks for Trump to dismiss Flynn after he learned that Flynn lied to Pence and others. “The question for you, Mr. President, is why you waited so long to act after you learned Flynn (through your VP) had misled the country?” Adam Schiff, the ranking member on the House Intelligence Committee, tweeted this morning in reply to Trump. Schiff also noted that Yates could shed light on the key questions surrounding Flynn’s call with Kislyak. “The public should learn a lot more about WHY General Flynn wants immunity when Sally Yates testifies before the House Intelligence Committee,” Schiff said. Last week, Devin Nunes, the chairman of the House Intelligence Committee, cancelled a hearing, scheduled for Tuesday, at which Yates was to testify, and the two congressmen have been negotiating whether and when it will be rescheduled.

Why Trump would encourage an immunity deal for Flynn is puzzling. Some commentators suggested that Flynn wants immunity to testify before Congress because it could complicate any Justice Department case against him. Alex Whiting, at the Just Security blog, noted that Flynn’s lawyer may be hoping that “Flynn gets immunity, his testimony in Congress gets aired and reported everywhere, and it becomes virtually impossible for prosecutors to bring a case against him.” This could be the ploy that Trump is hoping for, and it will be worth watching to see whether Nunes agrees that Flynn should testify before the House with a grant of immunity.

But if the Justice Department offers Flynn immunity, that would be different. After Flynn’s phone call with the Russian Ambassador, Putin announced that he would not retaliate against Obama’s actions. Soon after, Trump issued a celebratory tweet. “Great move on delay (by V. Putin),” he wrote. “I always knew he was very smart!” Immunity from Justice Department prosecutors could be a sign that the story Flynn has to tell is far more worrying for the White House than anyone imagined.