She seems miscast as Mata Hari, this quiet bookworm still in school at 41, with her formal, flawless manners and her closet full of brown clothes.

On the surface, Maria del Rosario Casas Ames is the kind of woman unlikely to attract special notice, and when the FBI led her away from her suburban dream house in handcuffs, the neighbors watching through binoculars were dumbfounded: What could she possibly have done?

They now know that Ames and her CIA husband, Aldrich Ames, are accused in one of the biggest espionage scandals in U.S. history. But for the Ameses' neighbors, and many others, the contradictory images of the woman behind the international headlines linger.

Apparently acting on the advice of the couple's court-appointed defense team, relatives and close friends of the Ameses' have refused to comment publicly, leaving the instant biographies to an odd assortment of casual acquaintances, disgruntled household help and long-ago teachers and classmates.

What begins to emerge is a portrait of a gifted scholar, born and raised in Colombia, with upwardly mobile parents active in politics and the arts. As a girl, she loved music, horseback riding and bullfights and dreamed of becoming a writer. A 32-word biography in her high school yearbook noted one thing she hated: hypocrites.

"She was a very critical student in the sense of never taking sides with any particular system," said Carlos Gutierrez, who was her thesis director in Bogota and still considers himself a "very good friend."

The devoted oldest daughter of three children, Rosario "Rosa" Casas lived at home until she was nearly 30, except for one semester at her father's alma mater, Princeton University. In 1983, by virtue of her family's political connections, she became a civilian employee at the Colombian Embassy in Mexico City, assigned to cultural affairs.

Aldrich "Rick" Ames, separated from his first wife, already was posted to the U.S. Embassy there as a CIA officer recruiting Soviet spies. Less than a year after she arrived, Casas became a paid informer for the CIA, according to the criminal complaint against her.

The thick affidavit does not explain what kind of information she allegedly supplied or whether she became Ames's lover before or after he put her on the payroll. But when Ames was transferred back to Washington in 1983, Casas quit her job and followed. They married on Aug. 10, 1985, at a Unitarian church in Northern Virginia.

In late 1990, during a brief stint as the family's live-in housekeeper, Albert Andrew chatted with Rick Ames on a Saturday afternoon while they watched television. Andrew was curious. "Mr. Ames," he recalls asking, "how did you meet Rosario?"

"He gave me a kind of a smile and said, 'Someday maybe I will tell you,' " said Andrew, 37. Although he remembers Rick Ames and the couple's small son fondly, Andrew expressed bitterness and contempt for Rosario Ames, who fired him "for no reason at all" after just three months.

"Mrs. Ames was wearing the pants in that family," Andrew said in a recent interview from the Laurel home where he is staying. "He never responded, never talked back. She used to call him stupid."

According to investigators, Rosario Ames took the lead in numerous conversations about her husband's counterspying, nagging him about details of how he would drop off secret documents or collect cash from handlers. In the transcript of one purported call, she calls her husband "honey" in one breath and then an expletive in the next.

Prosecutors have not said whether Rosario Ames personally passed along to the former KGB any of the classified CIA material her husband allegedly kept on numerous computer diskettes at home. She is, however, alleged to have been a greedy co-conspirator who enthusiastically aided and abetted after discovering her husband's secret by going through his wallet in 1991.

Through their high-profile lawyers, the Ameses are fighting the charges against them. Both remain jailed without bond in Alexandria, facing the possibility of life without parole if convicted of treason.

Despite the hot tub out back, the Jaguar in front and the state-of-the-art kitchen she seldom used, Rosario Ames was not generally considered flamboyant or ostentatious. The couple told others that she had inherited money from her family.

Her father, Pablo Casas Santofimio, was a mathematician and Liberal Party politician who served as a state senator before his death in 1982. Her mother, to whom she remains very close, is a bohemian patron of the arts. According to various Bogota publications, Cecilia Dupuy de Casas is an avid fan of Cuban music and dance and travels frequently to Havana.

Last year, according to the Colombian magazine Semana, Dupuy spent three months in a Havana hospital recuperating from a leg injury and later told friends that Fidel Castro dropped by to meet her while he was visiting an ailing baseball player.

When Rosario Ames attended the prestigious Universidad de los Andes in Bogota in the 1970s, her mother did too, taking many of the same classes and graduating with her daughter. The two then taught at the university; the daughter, who speaks five languages, lectured in Greek, Latin and literature, and her mother taught Spanish.

The FBI says that some of the $2.5 million the Ameses allegedly pocketed from the Russians went to buy a four-bedroom apartment in Bogota for Rosario Ames's mother and younger brother. Two of the bedrooms, according to local press accounts, are stuffed with books and antiques she sent from Washington. The Ameses also own a pied-a-terre in Bogota and an oceanfront ranch, where they planted two acres of coconut palms.

In their North Arlington neighborhood, even before the Ameses moved in, word quickly spread that the family had paid $540,000 cash for a gray colonial. When neighbors heard that the buyers had ties to Colombia, "well, I think you can imagine what we thought," said Tommye Morton, who lives across the street with her husband, John.

The Mortons quickly discovered that the newcomers were "this lovely family." Rosario Ames stood in quiet contrast to the affable Rick Ames, other residents of North Randolph Street recalled, but both were well liked. When Christmas came around, Rosario Ames gave her neighbors expensive bonbons. When Morton's first romance novel was published, the intellectual Ameses patiently stood in line at a local book-signing and congratulated her with a box of chocolates.

Not long ago, Morton recalled, her husband had an accident one Saturday afternoon on nearby Old Dominion Drive. The Ameses passed by and noticed John Morton's maroon Cadillac on the median strip. By the time his wife arrived, the couple had Morton, shaken but uninjured, waiting in the passenger seat of their Jaguar, with Rosario Ames anxiously hovering over him. "I think you ought to take him to the doctor or hospital," she urged Tommye Morton.

The magazine Semana, after interviewing friends and acquaintances in Bogota, concluded that for a child of the '60s, Rosario Ames had been remarkably "immune to marijuana, the Beatles and rebellion." At her private American high school in Bogota, the straight-A student was voted most likely to succeed. The 1969 yearbook also recalls her favorite expression: "How aesthetic!"

Academic achievement remained paramount to her, and even a decade after she left the Universidad de los Andes, Rosario occasionally would check in with former professors or advisers to report on her latest studies. As a mother, she worried about finding the right kindergarten to challenge her only child intellectually.

The Ameses told neighbors that getting the boy into one prestigious Alexandria school was tantamount to winning admission to Harvard. After filling out a myriad of forms, submitting to interviews and having their son tested, the Ameses landed him a coveted spot in that school's kindergarten, then pulled him out before September even ended.

"You know, it was just too much for him," Rick Ames told Tommye Morton when they met at a block party last fall. "He got stressed out."

Her former housekeeper and nanny have alleged that Rosario Ames sometimes mistreated her 5-year-old son. Yet the child's doctor, Mildred Barber, appeared in court last week as a character witness and called Rosario Ames "one of the most outstanding and loving and caring mothers in my pediatric practice."

Others have described both parents as indulgent. Guests at one of the Ameses' infrequent cocktail parties remember them beaming even as their son, clad in his cowboy outfit, noisily shot at the company with his toy gun.

For an allegedly covert couple, the Ameses were surprisingly sociable. He regularly attended meetings of the homeowners association, listening to park rangers lecture about local nature trails or to discussions about the Neighborhood Watch program to prevent crime. She appeared to be the dutiful wife at her husband's high school reunion, and she attended the surprise birthday party for a neighbor she rarely saw and, remembering the woman's love of gourmet cooking, gave her an elegant little book of Provencal recipes.

"She always looked very nice," said Tommye Morton, who like others on the street considered her neighbor well-to-do. "She wore lots of beige. Beiges and browns. No furs that I saw."

Albert Andrew tells a different story, insisting that his former employer went shopping and "brought home something new every day," usually jewelry or clothes from a tony store.

Regardless, Rosario Ames's natural habitat was the ivory tower. Until her arrest two weeks ago, she was working on a doctorate in philosophy at Georgetown University. At home, she would seclude herself in her upstairs study, learning German so she could better understand a favorite philosopher, Georg Hegel, who believed art was the highest form of expression.

Gretel Wernher, a former college instructor in Colombia, recalled, "She was a very conservative person. She always followed the instructions of her teachers. As a teacher herself, she was appreciated but not unforgettable, if you know what I mean. She was very formal."

Although the FBI said Rosario Ames initially cooperated after her arrest, she has not signed a formal statement. In court, when prosecutors read a note purportedly written by Rick Ames describing his wife as "very supportive" of his clandestine activities, Rosario Ames simply shook her head.

Back home, the headlines were calling her "The Colombian Mata Hari" and "The Spy Who Came In From the Tropics." Sitting in an Alexandria courtroom in her jail clothes, Rosario Ames complained of the cold before a bailiff brought her a coat.

As she sat listening to the list of accusations against her, the only thing observers could be certain she felt was that small, sudden chill.