He came in just three minutes before the ceremony started, and as soon as he appeared in the doorway, the cameras in the press gallery began buzzing like a nest of angry insects.

Richard Nixon had returned, and though his daughter Tricia walked with him, he had returned -- in a greater sense -- still very much alone.

His face solemn, his complexion almost waxen in the television lights, Nixon appeared tense but controlled as he walked somewhat stiffly to his seat behind President and Mrs. Carter and next to former First Lady Betty Ford.

And as the ceremony progressed and tributes poured out to Hubert Humphrey as an "uplifting symbol," and a man "with a heart so filled with love there was no room at all for hate," Nixon stared straight ahead, expressionless.

Here, in the city where he himself had seemingly won so much and yet in the end lost everything, he had come to honor an opponent who even in defeat -- in 1968 and in his last battle against cancer -- seemed somehow to have won.

Nixon traveled to the Capitol yesterday by Secret Service motorcade from a secluded estate in Fauquier County, Va., where he spent Saturday night and from which he was scheduled to depart today at midmorning for Dulles Airport and a return flight to Los Angeles.

It was his first appearance in Washington since resigning the presidency 3 1/2 years ago.

The estate, owned by the late U.S. District Judge Thurmond Clarke of California, is located in The Plains, Va., more than an hour's drive from Washington. Where Nixon was to stay had been kept a secret from all but a few of the former President's closest associates.

Clarke's widow lives in Corona del Mar, Calif., and Nixon was apparently staying alone on the property with his Secret Service contingent of 10 agents.

Nixon arrived at the Capitol yesterday at about 10:35 a.m., accompanied by his daughter, Tricia Nixon Gox. He was wearing a dark blue suit and tie and appeared grimly determined as he entered the Senate entrance to the building and mounted the steps to the Capitol corridors.

Mrs. Cox, dressed in a dark fur cap and jacket, and a black print dress, looked both sad and a bit frightened.

The former President was escorted to the office of Senate Minority Leader Howard Baker, where he met briefly with former President and Mrs. Gerald Ford, former Vice President and Mrs. Nelson Rockefeller and former Secretary of State and Mrs. Henry Kissinger before entering the Rotunda.

In the chamber itself, in his end seat on the second row of the 11-chair section reserved for the highest dignitaries, the former President was at times lost in the shadows cast by a military guard standing next to First Lady Rosalynn Carter.

At other times, he appeared lost in his own thoughts.

When the voice of Metropolitan Opera baritone Robert Merill singing "Ave Maria," rose powerfully over the crowd ranked around the flag-covered casket, President Carter leaned forward, smiling slight, intent on the music.

Muriel Humphrey clasped Vice President Mondale's hand while violinist Isaac Stern sat, eyes closed, silently fretting notes of the tune on his Stradivarius.

But Nixon sat impassively, seemingly removed altogether, even from his daughter who stood solomnly behind.

As Mondale began speaking, Mrs. Humphrey turned in her seat to acknowledge the presence of those seated in the row behind her, speaking quietly to each one. When she turned to Nixon he returned the greetwith a shy, self-conscious smile.

Nixon apparently decided on his own to come to the ceremony. Frank Nordy Hoffman, the Senate's sergeant-at-arms, said he was accompanying Humprey's body back to Washington on Air Force One shortly after the senator's death had been made public when he received a phone call from his office.

He said the office had received a call from Nixon aide Jack Brennan, who said that Nixon wanted to come to the ceremony and "they wanted our reaction."

"The only reaction that mattered," Hoffman said, was that of Mrs. Humphrey, who said it would be "such an honor" to have Nixon, and Hoffman said he passed that word along to Brennan.

Hoffman said the protocol of where and how to seat Nixon was no problem. "Our only real concern," he said was for the (Humphre) family."

In their Humphrey eulogies, both Carter and Mondale took note of Nixon's presence.

Mondale said the fact that Nixon, Ford and Lady Bird Johnson were present served as evidence of "the love and respect" in which Humphrey was held by politicians of all views.

Carter, noting that Humphrey was a forgiving man, recalled that when he lost the 1968 election to Nixon "without bitterness he gave his support to the new president."

And at the end, when President Carter and Merill led the audience in "America the Beautiful" Nixon joined the singing and moved forward hesitantly afterward to greet and hug Mrs. Humphrey.

Then the former President was escorted away. He stopped briefly in Baker's office again, chatted a short time with Ford and Kissinger, and then -- as one motorcade carried Humphrey's body to Andrews Air Force Base and another carried Carter back to the White House, a third zipped Nixon off to Virginia.

Richard Nixon wanted, once again, to be alone.