Mary Michael Calcutta was a vibrant 25-year-old, a part-time cake decorator who had grown restless living in her parents' home in Highland Park.

She wanted a change. A fresh start. An adventure.

She found it in the heat of Houston, Texas, where she took up country western dancing, took a job at a bank and settled into the Orchard Apartments, a sprawling complex full of lively young singles.

It was the late 1970s, and Houston was booming with newcomers, who, like Ms. Calcutta, sought opportunity.

"She wanted to get out of a rut, not just be in Pittsburgh, doing what she was doing," said her older brother, Jim Calcutta. "There was a whole world out there, and a lot to be experienced."

And, unknown to Ms. Calcutta, there was a lot to be feared.

Thirty years ago this month, Ms. Calcutta was found dead in her apartment, slashed and stabbed in a killing that shook the city's most experienced detectives, horrified her friends and family -- and remains unsolved. She was 27.

Those close to Ms. Calcutta -- in life and death -- remain haunted three decades later and say their quest for answers is hardly complete.

Initially, police focused on a boyfriend as a person of interest, but never found enough evidence to make an arrest. The investigation was passed to a cold case squad.

"Each year, it gets rougher knowing someone is out there, getting away with it," said Ms. Calcutta's younger brother, Fran. "You just can't let something like that go."

Ms. Calcutta was a middle child in a family of six siblings who grew up on Beverly Place in Highland Park. She was a daughter of Joseph, an assistant to the family of former Alcoa President and Chairman Roy A. Hunt, and Margaret, a pediatric nurse turned stay-at-home mom.

Faith was important to the Italian Catholic family. Sundays were spent in church and Ms. Calcutta graduated from the all-girls St. Raphael Catholic high school.

One of her closest friends was Beth McKinstry, who grew up on the same street. The girls threw slumber parties and went to movies, and they stayed close after high school. Ms. Calcutta went to work instead of college, taking a string of temporary jobs and decorating cakes as a hobby on the side.

One weekend, she visited a girlfriend in Houston and was smitten with the city. She called Ms. McKinstry.

"She said, 'Guess what, I found a really good job in Houston,'" Ms. McKinstry said, recalling their conversation. "'And it's not a temporary job.'"

Ms. Calcutta made plans to leave Pittsburgh, where her parents were used to their children leaving the nest. Ms. Calcutta's older sister, Sister Margaret Ann Calcutta, left home as a teenager to become a nun, and her brothers had moved around the country for their work.

Ms. Calcutta's parents were proud, but concerned.

"My mother and dad certainly didn't want her to go," Jim Calcutta said. "Mary was pretty strong-willed. She said, 'I want to explore new things.'"

In Houston, she joined a group for Christian 20-somethings and made friends. In the days of expensive long-distance phone calls, she spoke to her family once a week, sent cards home for birthdays and returned on the holidays.

She never expressed fear for her safety until one day in late July 1979, when a 33-year-old woman's nude, headless body was discovered in the Orchard Apartment complex where Ms. Calcutta lived. She stayed with a friend for a few weeks, then went back to her apartment.

"She called and said she was frightened, there had been a murder in her [complex]," Ms. McKinstry said. Ms. Calcutta pushed a bookcase in front of the door and vowed to her friend that she would not open the door for strangers.

Two weeks later, on Aug. 10, a "male friend who said he came to visit Ms. Calcutta" discovered her dead on the bathroom floor, according to an article published in the Houston Chronicle. She had been stabbed with a butcher knife from her own kitchen.

It was a bloody summer in Houston. Police would investigate 17 homicides the weekend of Ms. Calcutta's death. There were several "copy cat" killings that summer, an investigator said, involving women who were viciously stabbed. But the alarming Orchard Apartment slayings became the stuff of urban legend, shaking residents for years to come.

Both of those cases remain unsolved.

After the killings, a Houston homicide lieutenant advised "women who live alone or with female roommates to make darn sure their doors and windows are locked," according to the Chronicle.

Police at the time believed the Orchard Apartment murders were connected, though the victims were vastly different. Ms. Calcutta's family is convinced she was killed by someone she knew. Retired Houston homicide detective Jim Binford would not identify the person who attracted the attention of investigators.

"We had a person of interest probably three days after the murders occurred, but you have to have evidence," said Mr. Binford, who kept Ms. Calcutta's case file on his desk for 25 years. He still can't get the case out of his mind.

Police considered Ms. Calcutta to be an innocent victim -- a good Christian girl "cheated out of about 75 years of life by somebody who was angry with her," Mr. Binford said. He described her attacker as a bright, organized killer, "the smartest guy in the room." He might still be alive.

"Mary Calcutta died harder than any woman I had worked on," Mr. Binford said. "She was the flower that grows in the crack of the sidewalk, that blossoms, and you know it's a matter of time before it gets stepped on and broken up."

Many nights, Mr. Binford waited on the roof of the apartment complex wearing night vision goggles, seeking clues or signs of her attacker. As years passed and the case remained unsolved, he asked countless detectives and psychologists to review it.

"Thousands and thousands of hours were put into the Calcutta case. We worked every clue we could possibly work," Mr. Binford said. "We chased lots of rabbit trails. You just don't clear all cases."

Fran and Jim Calcutta went to Houston to tend to their sister's belongings and clean her apartment. Jim offered a $25,000 reward for information leading to an arrest.

Back in Highland Park, her parents kept her framed photograph in their dining room, but grew resigned that police might never catch her killer. They rarely talked about the crime; it was too painful. They both died years ago.

"Their hearts were broken," Jim Calcutta said. "You could see it on their faces. We can't change it. We can't keep reliving it. It's not healthy for the survivors."

But the case lingers in the siblings' minds and in their conversations, especially at reunions, when they flip through photos and remember happier times.

"You look at some of the pictures from when we were little and you just wonder how she would have turned out," Fran Calcutta said. "You're thinking, 'What if?' "

The case still attracts interest and has found its way onto online discussion boards.

"With all this new technology available, I hope it is just a matter of time before the person who did this is arrested," wrote one poster.

"The person responsible, if these are the crimes of one person, should not go unknown for the sake of the families and loved ones who could find some measure of comfort from the truth," wrote another.

"I like to see it kept alive," said Fran Calcutta, who sometimes trolls the blogs in search of new information. "Who knows? Maybe somebody will step forward."