Two years ago, Tammy Lynn Giles of Waldorf, Md., was a bright, outgoing student, a Girl Scout and the family tattletale. Then in January 1984, she mysteriously disappeared from home, an event that her family said changed her behavior suddenly.

After she returned a week later, Giles reluctantly told a social worker that she had been raped during the week she was gone.

"She was in over her head and she got into a situation she couldn't handle. Since then, there's been nothing but trouble," said her stepfather, a D.C. police officer who married Giles' mother when Tammy Giles was 2 years old.

On Aug. 4, the escalating problems of Tammy Giles, now 14, burst beyond the private realm of psychiatrists, social workers and family when she disappeared with Michael Justin Fitzgibbon, a 22-month-old boy for whom she had been baby-sitting.

During the next six weeks, she and the child hitchhiked from Pennsylvania to Phoenix to Dallas. On Sept. 14, Giles surrendered to police in Pittsburgh and directed them to a seedy motel in Dallas where she had left the child in the care of a woman. Michael Fitzgibbon was reunited with his family last Sunday.

Charged as a juvenile with kidnaping and abduction, Giles was brought back to Charles County and is now in custody at a youth facility in Baltimore County, awaiting the outcome of her case in juvenile court.

Her family views her confinement and the intensive counseling she is likely to receive as a blessing. They said the bubbly Girl Scout who participated in the gifted-and-talented program at her middle school had become a tough-talking truant and habitual runaway -- withdrawn, rebellious and attracted to a rough, older crowd. During the past two years, Giles, who capitalized on the fact that she looks older than her years, ran away from home a dozen times for extended periods. Sometimes she ended up as far away as California.

Baffled, her parents initially tried talking to her and restricting her privileges, her stepfather and an older sister said. They admitted her to an expensive psychiatric hospital, where she remained for a month, and they took her to a string of psychiatrists and psychologists. They also sought advice from government agencies; her stepfather said a social worker with the Charles County Department of Social Services told them that until Giles committed a crime, there was little his agency could do.

Her stepfather, a 15-year police veteran who did not want to be identified in order to protect the family's privacy, said the latest episode has changed the situation. But no one has been hurt, he said, and the family is hoping Giles will get help.

"She needs some confinement," said her stepfather. "She needs somebody to talk to her and get close to her and get inside. We feel better about her now than we have felt in almost two years."

Tammy Giles' home is a green, split-level house on a tree-shaded street in St. Charles, a middle-class development of about 22,000 people just south of Waldorf. She lives with her stepfather, whom she refers to as "Dad," her mother, who has declined to talk to reporters; a sister, 18, who works as a hairdresser, and her 11-year-old half brother. She sees her natural father infrequently; he also is a police officer.

As a small child, Giles, blond-haired and blue-eyed, was outgoing and attractive, the family said. She belonged to swimming and soccer teams and enjoyed going to Baltimore Orioles' baseball games with her stepfather and brother.

"It's strange," said her sister, who also did not want to be identified. "I was always the bad one and she was the good one. She was a real tattletale, always trying to get me and my brother in trouble. She was so close to my parents, I was jealous."

The approach of adolescence brought routine growing pains. Authorities say there were minor disciplinary problems at school. But until the time she said she was raped, her stepfather said, she had never really run away from home. Her most serious disappearing act until that time was when she hid briefly in the bedroom closet in a neighbor's house when she feared confrontation with her parents over a bad grade.

On a snowy evening in January 1984, Giles, then 12, was spending the night with a girlfriend, her stepfather said. Somehow, they became involved with two 18-year-old men, according to Giles' account to police. Giles then disappeared for a week.

When she returned, a social worker pried from her the story of her rape, the family said. Charges were filed against the two men, but the case was never prosecuted. Giles' stepfather says she was afraid to testify about the rape and dropped the charges; police sources, who confirm that she was the victim of an assault, say the case faltered because it was unclear to what extent Giles might have encouraged the men.

"She was like a different person after that," said her sister. "She didn't care about herself anymore. She ate a lot of junk food, just sat around. She wouldn't tell anybody anything. She did things for no reason -- running away, skipping school.

"We had been very close, and then we began to grow apart."

That February, Giles' parents placed her in the Westbrook Psychiatric Hospital in Richmond, a private facility that serves about 200 patients ranging from the severely disturbed to the mildly depressed. The rates vary from $215 to $332 a day, depending on the level of treatment. Giles stayed there a month.

"I don't know how many thousands of dollars I paid out," said her stepfather. "They suggested she stay longer. They said it would cost $50,000 to give her all the treatment she needed. We didn't think it was doing her much good."

"When she came out," he said, "she was in a pretty good mood. We made a lot of adjustments. We all sat down and said, 'We do this and you do that, we did things wrong, and you did things wrong, but maybe we've learned something.'

"We've never been beaters or anything like that. We've always dealt in restrictions, like, 'Okay, no phone calls,' or 'You're grounded.' After a while, it didn't even faze her."

Her disappearances followed no pattern. Sometimes she took clothing with her; sometimes she did not. Sometimes an argument preceded the disappearance; more often than not, she would leave just when her behavior had seemed normal.

"Her grandmother was visiting one time," her stepfather said. " Giles went to the store and didn't come back. And she loves her grandmother. One time, she spent the night with a girlfriend and they woke up the next morning and she was gone."

She hitchhiked to Florida, to California, to Texas and to New York.

"She's smart. That's why she never got hurt, I think," said her stepfather. "She's very manipulative and she knows how to work truck drivers. She was out for adventure, I guess -- why stay here when she can go lie on the beach in Florida?"

"She told me she always met somebody and they took care of her," said her sister. "I couldn't do some of the things she's done. It's like she lived in a dream world."

School became a nuisance. "She was the kind of kid I envy," said her stepfather. "She was bright and she could absorb enough to get by just by being there and not opening a book." Heavy absences took their toll, however, and she flunked the eighth grade at Benjamin Stoddard Middle School in Waldorf last spring.

Her family does not know the whole story about her disappearance with Michael Fitzgibbon; their attorney has advised them not to talk about what little they know or suspect.

Her stepfather and her sister say that she had not argued with family members before she left.

Sharon Fitzgibbon, the baby's mother, said that Giles volunteered to baby-sit for Michael when his 15-year-old sister, who was in charge of the baby, wanted to spend the night with a friend. Fitzgibbon was away for the weekend.

Giles' family finds the matter puzzling, however; they said Giles barely knew the Fitzgibbons and had been to their home only once before.

"I don't know what she was doing baby-sitting," said her stepfather. "We don't let her baby-sit. She was in no shape to baby-sit."

That Sunday night, Aug. 4, Giles telephoned her mother from the Fitzgibbon apartment, her stepfather said. She gave no hint that she was planning to leave with the baby, but when Sharon Fitzgibbon got home the following morning, both were gone.

Almost six weeks later, after a nationwide alert for the pair and reports of numerous sightings, Giles telephoned Pittsburgh police from a phone booth near police headquarters; authorities say that she wanted to turn herself in. Giles reportedly said she had left Dallas for a few days in order to visit a former boyfriend, Mark Anthony Flick, who had been released from prison on Sept. 13, the previous day. Flick, 23, served 11 1/2 months for a parole violation on an original offense of receiving stolen property. The two initially met more than a year ago at a D.C. bus station, a Charles County sheriff's deputy said.

Michael Fitzgibbon appeared to be in excellent health when he was returned to his family. His mother said he had a bad case of diaper rash, but he had gained weight and spoke more coherently than he did before he vanished.

"Tammy didn't hurt the baby. She loved the baby," said Giles' stepfather.

Giles' sister said Giles told her she had tried to toilet-train the child while they were together, taught him several new words and encouraged him to give up his bottle.

"She loves kids," said the sister. "Her ultimate dream is to have a baby."

Deputies returned Giles to Charles County early Wednesday. At a preliminary hearing that day, she was composed and looked grown up in a multicolor, striped dress and high heels. At her next hearing, scheduled for Oct. 7, the judge is to decide if there is sufficient evidence to continue the case.

"She was fairly relaxed," said her stepfather about her first courtroom appearance. "I don't think she realizes what she's done."

The judge, while refusing to comment specifically on Giles' case, said he favors long-term counseling for juveniles.

"What happens next is up to her," said her stepfather. "Counseling can only do so much. You've got to want to be helped, and we've got to help her have that strength. She really can be the best kid in the world if she wants to be."