Sidney Rittenberg, American mystery man of Peking, smiles thinly, light glinting off his thick, dark glasses. This is his tale:

January 1964. He was sitting with Mao Tse-tung in the same chairs Mao and Khrushchev has sat in years earlier. Mao recalled how Khrushchev had been going on about establishing a joint Sino-Soviet fleet along the China coast.Mao said, well, why don't you take the whole coast? Khrushchev looked at him uncomprehendingly. But what'll you do? he said. Oh, said Mao, I'll go back to Yenan and start the guerrilla war all over. But, remember, the Chinese people will one day drive the new aggressor to the sea . . .

It is a story never before told in the Occident, says Sidney Rittenberg, falling quiet.

He went away at 23. He is 57 now, balding and gray, this man who has sat with Mao, who was a protege of Chou En-Lai, who was imprisoned by the Gang of Four, who has a Chinese wife and Chinese children and a home in Peking and not only a job there, but roots, his stake. But there are other roots, too, in Charleston and Chapel Hill. And it is to get back to these, plus see what water has passed under bridges he left behind, that Sidney Rittenberg has journeyed halfway around the world.

After 34 years in China, Sidney Rittenberg has come home: The return of the native.

He must feel a little like Rip Van Winkle. He smiles, nodding. His gaze floats toward a picture window and a fruit tree in soft spring blossom. He is hunched forward and his hands are clasped in front of him, elbows of his blue blazer resting on his gray slacks. He looks like an insurance man from Omaha.

"There was a note, only about this big," he says, making a small square window with his fingers, "in the middle of the People's Daily, saying Richard Nixon had gone on American television to resign because of Watergate. I was still in prison and I remember thinking, 'What in hell is Watergate?' I wondered if it wasn't some giant hydropower project. And I thought, 'President resign?' Why, I never heard of that. Is there a provision in the Constitution for it?'"

The voice carries only a tinge of magnolias and sepia-tinted long hot summers; but they are there, along with a certain curious gentleness - residual southern gentleness, maybe, tied to three decades plumbing the Oriental mind. No, not plumbing, Rittenberg says softly, just experiencing.

Next week Sidney Rittenberg, who works for the New China News Agency, will have his first homecoming in Charleston, where he grew up, in 36 years. Uncle Henry and Uncle Alvin and old classmates will be there. He is both scared and excited.

"Our family house was known as the yellow house on Orange Street.It was built by an ancestor before the American Revolution." Rittenberg's grandfather was a five-term legislator; his father was president of the Charleston city council.

He is silent. Perhaps his mind, instead of his fingers, is tracing the border of some creased family photo in a leather album. "I saw my mother in New York (two weeks ago) and she said she thought I was dead. I told her there was time when I thought I was dead, too."

He is talking of a dank cell-seven paces long, 3 1/2 paces across, with a little aperture in the bottom of the door for sliding the food through. Sidney Rittenberg lived in this cell, in solitary, for almost a decade, from 1968 to 1977, bereft of family, an enemy of the state and the Cultural Revolution and the Gang of Four-an accused spy. Later, Rittenberg will talk more of his two incarcerations, which in all lasted 16 years, but for now he just says, "I kept remembering a line from a poem, maybe Swinburne, maybe Rosetti: 'One eternity in six paces.' Oh, I didn't always feel like that."

The saga of Sidney Rittenberg is long and of Mandarin intricacy. It has to do with and Army private from a prominent South Carolina family, a brilliant linguist who went to China in 1945 with the U.S. Army Signal Corps, then tore up his discharge papers, though not his citizenship.

In a way, Rittenberg stands for a whole generation of World War II-era Americans and their fascination with China - with its hugeness, its distance, its strangeness. (That fascination has raged anew, of course.) He is one of those Americans who was inexorably drawn to China and the Communist revolution in the aftermath of the war and who simply never went home.

But Sidney Rittenberg's story is odder still: He rose steadily in the Chinese bureaucracy to become a leader in Peking Radio, a "foreign expert" with wide influence and respect.

For a time, until what he calls the "witch hunt" began, he may have been the most powerful foreigner ever to work in the government of Mao Tse-tung. He is still thought of today by many as the finest Chinese-English interpreter in the world. Recently, fully back in favor (with 10 years pay dropped on him in a lump), he did a simultaneous contrywide translation of "Roots" in two six-hour broadcasts.

Hot Dogs and Pepsi

Mrs. Rittenberg, a warm, smiling, moon-faced woman named Wang Yu-lin, has brought tea and cakes to the living room of the Northwest house where they are staying. At home, in their apartment in the Friendship Hotel, she drinks flower or grain tea; this, however, is English breakfast tea. She has been knitting a sweater with red yarn in a chair across the room. The sweater is for the couple's oldest daughter Xiao Chin, 22, a student at Peking Medical College. Xiao Chin has an English name, too-Jenny.

Mrs. Rittenberg says now, "Yesterday, we tried hot . . . dog." She says it and breaks up.

Her husband is laughing, too. "We gotit at a stand outside the Hirshhorn Museum. It was a hot dog with chili sauce and sauerkraut and it was delicious. There's nothing like it in China. They eat a lot of weenies, but the idea of putting mustard on one and sticking it in a bun hasn't been tried."

He nudges closer. Crops his voice, raises his brows. "And then we tried-and this is kind of seditious-Pepsi-Cola."

It is a mark of Sidney Rittenberg the man that, after all he has been through in his adopted country, the attainment of position, the Kafakaesque reversals, that he shows no bitterness, in fact can even joke about his bad times. He talks about them with a dispassion, a detachment. Mention the word "bitter" and he wags and smiles furiously.

"People here cannot understand why I'm not bitter. You see, I always had particular feelings about China-and about the rapprochement the Chinese people would one day have with the American people-that kept me from getting bitter. In prison it was just . . . a different fascination. It was a microcosm in the macrocosm. But you do see the sun in a grain of sand if you look close enough. And I think I understood in a cognitive sense that bitterness was the enemy. And the other enemy was self-pity. You say this to people in America and they think you're self-denying."

His first imprisonment, from 1949 to 1955, (he was accused of espionage), amounted to a house arrest. He got out, married Yulin, fathered four children, rose in the ranks. The inscrutable door clanged shut again in 1968. He refused to give in, renounce his citizenship, renounce his love for China.

"The very morning after the door clanged I somehow remembered it was George Washington's birthday. I began systematically that day and every day afterward to do physical exercises in my cell. I had the idea that all this would be cleared up and by God I was going to be in shape. I was going to show them that American friends of China were no softies. I was going to survive."

This phrase, "American friend of China," is sprinkled throughout his conversation.

An odd thing now happens: The phone is ringing nonstop and Rittenberg, having answered it several times already, goes across the room to take it off the hook. The telephone company's automatic warning comes on, flooding the room. Yulin looks alarmed. She talks in high, staccato bursts to her husband, in Chinese. He answers back in Chinese, apparently trying to soothe.

"She doesn't understand. She thinks it's a criticism. She keeps saying it: 'criticism.' She thinks the phone company is trying to tell us. It would b e that way at home."

There was another cultural surprise-for him-the other day at the Smithsonian, he says. "There was a little boy, maybe 4 or 5, very cute and I couldn't resist reaching down to pat him on the head. He looked up at me with surprise and said to his mother, 'Mommy, Mommy, this man just put his hand on me.' Well, you couldn't imagine that happening in China. Every adult is Uncle or Auntie. A child would look up and say, 'Why, hello, Uncle.' This is a country with 900 million people."

Culture shock cuts in both directions. Rittenberg's impressions are by no means negative. He thinks Americans are more tolerant racially than when he left. (When Yulin went shopping in New York, several strangers came up and offered to help her out.) There is less eye pollution along the highway, he thinks. The phone doesn't start ringing as early as it did at home. "At home it starts about 6:30 or 7, beacuse people go to the office much earlier."

New Hope

Yulin works for Peking Radio as a translator. She usually rides her bike. Rittenberg works for the New China News Agency, as a translator and polisher of texts. His stature is such that a car now often comes for him. He can savor the irony.

When he was imprisoned, his wife did three years of labor in camps. The children went to stay with relatives. "Now there's a formal conclusion on my case that says I was wrongly charged with espionage, and that I have a record of contributtion to the Chinese people."

Did they ever think he was CIA? "They never mentioned CIA, but I once did and the interrogator jumped." In California, in the Army, as a scheme for getting himself to the Orient, Rittenberg had applied to the OSS, forerunner of the CIA, Somehow, it is difficult to imagine him as a double agent. Sidney Rittenberg is restless, alert, intense, his mind rigorous and quick. He isn't the least sinister.

Not that he is innocence and simplicity, either. There is something hidden, something veiled, about sidney Rittenber.And the southern courtliness can be a seductive blind. Once, as a director of Peking Radio, Rittenberg had to pass approval on regular denunciations of America. He sidesteps this when you ask about it. "I was more advisory," he says, letting it go at that.

But how did his love for China first develop? He thinks it was the lanluage.

"I just drank it in. The country seemed to be a place that offered new hope. I felt America was one of the newest countries in the world and here we were showing signs of old age-cynicism, weariness, distrust of the future. I don't know, the Jeffersonian, Jacksonian dream seemed to be fading. I think I felt that if the new socialist changes in China could be demonstrated to the U.S. . . ."

He trails off.

Did he ever think of taking out Chinese citizenship. He is holding a glass of ice water against his cheek. "It always seemed to me if you did that, the whole meaning of your life would go down the drain."

His friendship with Chou En-lai, whom he first met in 1946, sustained him through the bad years. Later, when he had risen at the radio, Mao's wife, Chiang Ching, accused him of a plot to sabotage Mao and overthrow Chou. She is the one, he thinks, primarily responsible for his purging. "I had let myself get vulnerable for her propaganda to the masses. She wasn't a woman, she was a fascist."

It is odd, this voice with its southern, almost Elizabethan, tunings and the conversation that keeps revealing such a knowledge of the inner sanctum of China.

He is asked about Vice Premier Deng Xiaoping and how his visit was carried in China. "Well, we all watched it on television every night. Our room was jammed. Everyone was very happhy about it. Except our children. They were unhappy about one thing: He kept taking out a prepared text. This is very unlike him."

Yulin: "Oh, but you must remember he's very old."

Rittenberg: "That's not it, honey.

He's very fast on his feet."

Sidney Rittenberg calls his wife "honey" a lot. When the photographer takes a picture, he makes sure she is sitting on the same level as he. "We don't want to upset the women's-lib faction."

Waht surprises Rittenberg most about his visit back to America after all these years is his reception. Everywhere he goes, people want to interview him. "It's still hard for me to realize what's so interesting. I had a tip-off as to how it would be when we were still in Peking and the 'Today' show called up to ask me on the show. I said to Yulin, 'I think this is only the start.'"

No Doubts

In Washington, Rittenberg is staying with an old college classmate from Chapel Hill, a government geologist. He's already had two reunions with classmates, in New York. "None of them had much information about me through the years. They'd pass around waht they knew." He seems to enjoy that.

Last year, Rittenberg established contact with his sister for the first time since his departure. "In her first letter she said, 'I always knew some things about you would never change.'"

One of which is that Sideny Rittenberg is going back to China. His tour here will last through June. There has never been a doubt, he says, that he would go back.

"Only if someone in America asked me to do a very important job would I stay. But I don't really expect that to happen."

When he gets home, he will resume his translating chores at the agency. The children will continue their schooling. Yulin will take up at the radio again. The seasons will pass.

"I never knew," he says softly,"the trees could be so pretty in spring. I had forgotten it, I guess. Charleston may be magical. It may make me very homesick for home." CAPTION: Picture, Sidney Rittenberg and his wife, Yulin, by Harry Naltchayan-The Washington Post; Illustration 1, 2, dragon-shaped jade ornaments