Michael Straight sinks deeper down in his armchair and stares balefully into the fire.

He's been over it all so many times before, four decades of this canker at the soul's root. As a communist dupe, he had betrayed first his country and then his friends: Was he a spy or merely spineless? But always his suffering had been private--until two years ago, when suddenly there it was: the whole squalid chronicle crackling across the front pages.

So "I wrote the book to explain myself, to purge myself," Straight says, each weary phrase dying to a sigh. And to rebut the press accounts that "represented me as a spy for Soviet Russia, which I was not. I felt I owed it to my children and my grandchild to tell my own story," although "it's not a story I'm very proud of."

At 66, the author, former editor of The New Republic and former deputy chairman of the National Endowment for the Arts, has groped again through the murk of memory to produce "After Long Silence," his "political memoir" just published by Norton--one of the most extravagantly unflattering autobiographies in modern memory. "I knew I had a debt to pay" to the British and American people, he says, and is ready to "take whatever blame they wanted to heap on me."

They have been heaping since March of 1981, when the London Daily Mail broke the story of his role in the spy scandal of the century: That it was Straight's belated confession in 1963 which led to the eventual unmasking of British art historian Anthony Blunt, then the queen's personal curator, as a Soviet agent.

Despite longstanding suspicions, there never had been hard evidence to tie Blunt to the treasons of Guy Burgess, Donald Maclean and Kim Philby--until Straight revealed that Blunt had recruited him to the communist underground in 1937 when both were at Cambridge. And more: acting under Blunt's directions, Straight had returned to America in 1937 and over the next four years, while working in the State and Interior departments, he met with and gave copies of his work to a Soviet agent named "Michael Green." Worse yet, he concealed his knowledge of Blunt and Burgess' activities until a routine FBI check for the Endowment post drove him to disclosure. Straight says he has encountered "absolutely no" social censure after his initial exposure in 1981, but the publication of his book has exposed him. William Safire has already fired off a salvo of contempt, but stopped short of calling Straight a traitor, if only because "no purpose or passion guided his double life." There will be more.

"The center of the judgment against me so far is that I failed to do anything with the information I had for some 25 years," says Straight, feeding the fireplace with newsprint between brooding pauses. "And essentially that's true. I'm not looking for praise--or for unjustified condemnation. I'm perfectly happy for people to say I was wrong or weak."

Weak. It's his explanation for why the son of one of America's most wealthy and prominent families (with a personality strong enough to become the first American elected president of the Cambridge Union, that formidable debating society and political incubator) would fall under the spell of the effete Blunt, agreeing--by not disagreeing--to aid The Communist International. "I lacked the will," he says. "I lacked the sense of self."

It's hard to believe at first, that this placid Bethesda squire in Shetland and flannels with the soft, still-boyish face barely chafed by time, snug in his Tudor enclave where J.R. the one-eyed dog guards the front door and a behemoth cat named Bananas pads under the centuries-old paintings, could lack a sense of self. Yet as he talks, Straight habitually defers to others for his ideas--punctuating his languid exposition with "historians say" or "no one now believes," reaching frequently for the small notebook he has filled with handwritten quotations--from Gide, Keynes, Koestler--about the movement which gave his life meaning. "The man who knows who he is remains an individual. I was submerging myself into a larger identity because I didn't know who I was. I had no roots, no separate identity. I didn't want one." He is slouching further now, wilting diagonally, hanging his right arm over the chair until the hand grazes the floor, voice sinking to a hospital waiting-room croak.

"I'd been transported from one country to another, I'd never had a father, my family was broken up--there was no continuity in my life of any kind. I wasn't held in place by tradition. I think tradition is very important."

His mother was a Whitney heiress and freethinker, his father an artist and diplomat. Together they founded The New Republic in 1914. (It would later provide their son with an occupation whenever he needed one: as a writer from 1940-41, publisher from 1946-48, and editor, 1948-56.) His father died in World War I (when Michael was 2), and his mother married Leonard Elmhirst, an iconoclastic English educator who convinced her to join him in founding a utopian academy in England. They moved there in 1926 and started Dartington Hall, where students grew their own vegetables, built livestock sheds, played bicycle polo and used unisex showers. By the time he was 12, Straight writes, he and his brother and sister "could not spell" but, "We were all too familiar with Freud's interpretation of dreams."

His family, too, proved eccentric: at teatime, his mother always "took two slices of brown toast . . . chewed on them until they were soft and mushy; then she took them out of her mouth and laid them on the window sill. The birds gobbled them up." His brother would become an English citizen and famous sports car racer; his sister, a celebrated actress. And Straight ("Do psychiatrists point out the innate submissiveness of the youngest child in each family?") drifted to the London School of Economics and then to Cambridge, where communism was in full philosophical blaze.

"In the '30s in Europe," he says now, "the nation-state seemed to be dead, a remnant of the past," and "the thing that moved me and my generation was internationalism as a way to replace the nation-state and offer peace and security to individuals." Moreover, "the First World War had killed off all the men of promise. The leadership in the political parties was abysmally bad, creating a vacuum into which a new sense of brotherhood emerged."

His closest friend was John Cornford, a devoted Communist who would die in the Spanish Civil War. And soon he was asked to join the Apostles, the secret intellectual society whose members included John Maynard Keynes, Burgess and Blunt, who became "my wise and valued adviser." The fact that such a large percentage of the group was homosexual, Straight says, was "an historical accident. You could argue that they were individuals who felt alienated in society, and that only through the transformation of society could they be accepted. But I don't think so. They were simply the most sensitive, most intelligent and most esthetic.

"It was characteristic of the Apostles that they attached enormous importance to human relationships." So when Blunt took advantage of Cornford's death to tell Straight that The Communist International was ordering him to return to the U.S. and "go underground," Straight acquiesced. Once in Washington, he needed a job. So "I went to see Roosevelt in his White House study." FDR "tried to think of some agencies that might want to take me on. He gave up." Straight's godfather sent him to Eleanor Roosevelt, who got him into State as an unpaid volunteer. While working there and later at Interior (a job he got through Tom Corcoran after Corcoran hit him up for $10,000 to bankroll Texas Rep. Maury Maverick's campaign), Straight met intermittently with the mysterious Green.

Was it treason? "No," Straight insists. "Treason is dealing with the enemy in time of war--and at no time were we at war with the Soviet Union." Was he a Soviet agent? Straight flatly denies it: "I never took any orders." But didn't he meet whenever asked? "I just acknowledged his presence and didn't repudiate him. He was aware from the very start that he couldn't give me orders, and didn't try." But didn't Green ask him for documents, and didn't he deliver? "Yes, but those were just my opinions." But the first report he wrote at State was praised by Dean Acheson and Cordell Hull. "Yes, but it was not information." But wasn't he in regular contact with opinion makers such as Corcoran and Ben Cohen? "Not really. I just sat in my office alone. I wasn't in the White House mess listening to what was going on."

Besides, what he gave Green, he says, "was very critical of Soviet policy," so unwelcome to Green's masters, Straight says, that "I'm convinced I sent him to his death." (Many foreign agents were liquidated under Stalin, but no one knows what happened to Green after he disappeared in 1942.) Why not simply stop meeting with him, then? Straight's voice--a cross-Atlantic accent like George Plimpton's without the lockjaw--grows even more exhausted. "It would have been the equivalent of desertion on the field of battle. Breaking not only with Blunt, but with John Cornford, cutting off all my ties."

Meanwhile he was meeting occasionally with Burgess, who one night in 1940 suggested that they "get in touch with our friends." At that point Straight knew that he was a Soviet agent, but he kept his secrets from everyone but his then-wife, Belinda Crompton (just as he would tell all to Nina Auchincloss, his present wife, before marrying her in 1974). "I became known in Georgetown and everywhere as someone who took an intense interest in others but never talked about himself." Then one day in 1951, he was shocked to meet Burgess on a Washington street. "I had learned only in 1949 that Burgess had been in intelligence during the war," he says, "and I believed he was then with the BBC." It occurred to him then, Straight writes, that if Burgess had known of American military plans in North Korea, and communicated that to the enemy, "Guy could have caused the deaths of many American soldiers."

Burgess assured him that the Chinese and Koreans already knew. But some analysts now believe that the slaughter of MacArthur's forces at the Yalu River in 1951 came about because a British Communist agent did just that. "Historians don't take that seriously," says Straight, reaching for a study to prove it. And as for Burgess' involvement, it's "absolute nonsense. The man was a discredited minor official of the British Embassy here--under suspicion, under surveillance as was Philby."

Still, "I was just outraged that he had lied to me." So he gave Burgess a rather generous ultimatum: " 'Look,' I said. 'We're at war now. If you aren't out of the government within a month from now, I swear to you, I'll turn you in.' " Some three months later, Burgess and Maclean fled to Russia. At that point Straight went to see a British official he knew well and offered information on Burgess. Straight says he was rebuffed. Ditto when he asked to have lunch with his cousin, Tracy Barnes, then deputy director of the CIA. "Ask me about Cambridge," Straight prompted hopefully. Barnes said he wasn't interested. "I needed one beckoning word or gesture to lead me on," Straight writes. "Without it I lacked the resolution to carry out my impulse."

Finally in 1963--after a decade spent in public interest work and writing two well-received novels for Knopf--resolution was forced upon him by the offer of the NEA chairmanship. (It was arranged by his mother-in-law, who was "convinced that I needed some job to keep me occupied.") Thinking of the FBI check, Straight writes, his past suddenly came gurgling back as "a disposal regurgitates its half-digested meal of garbage." So he went to Arthur Schlesinger, withdrew his name from the NEA post, and admitted all. (He told Blunt a different story when they met in London after Blunt's confession in 1964. "Why did you act when you did?" Blunt asked. "Because of the arts," Straight said.)

He was interrogated first by the FBI, then by British intelligence, identifying various government members who had been Communists in the '30s. "It is a role that is despised in every country and in every context," Straight writes. "It runs counter to a determination that we all share--not to inflict pain upon others."

Although he eventually served in the NEA post from 1969 to 1977 and took on a score of worthy projects, Straight says he still has never developed a true sense of self. His greatest accomplishments, he feels, are "the two novels I wrote--that's what I like best." He might write again, but everything depends on the reaction to his memoir. "This situation now is so integral to my being that I'm just paralyzed. I have no plans" until the expected flare of blame subsides. Meanwhile, "I continue to feel that I'm living at an economic level that does not reflect my contribution to American life." He brushes a hand to indicate the easeful, overstuffed elegance of this sitting room, "these pictures," including the striking northern French painting of a beggar ("Blunt wrote about that"), his inherited wealth. "I think that's unjust. It continues to bother me--but not enough to give it all away."

The melancholy deepens. And apropos of nothing, or everything, Straight says, "The epitaph I'd put on my gravestone" is a line from a Russian poet: "They will not ask us, Have you sinned?, but Did you love?"