AFTER HIKING THROUGH a wooded area, two West Philadelphia residents took a shortcut across railroad tracks. They were headed down an embankment when they saw it.

At dusk, the white bone looked bleached amid the underbrush. At first, they thought it was a dog's bone, they told Detective Luis Velazquez.

As they got closer, they saw the skull.

The 31-year-old Chestnut Hill College woman was "shaken up," said Valasquez.

Her boyfriend, a 29-year-old Rutgers student, called police at 6 p.m. March 11, setting off the arduous task of solving a mystery.

Behind every skeleton is a story: Was this a man or a woman? Did the person die violently, or had he or she been missing for years?

Of the 5,600 deaths reported in Philadelphia each year, the remains of 2,300 are brought into the medical examiner's office, while others remain in hospitals until an undertaker picks them up.

Of the 2,300 at the medical examiner's office, the remains of about 300 become a mystery each year. Most are identified within a couple days, but there remain up to four each year for which investigators don't have a clue.

Could this be one of them?

The work began.

Police posted yellow "Do Not Cross" tape around the skeletonized remains about 15 feet from the railroad tracks and near a hospital garage on University Avenue near Civic Center Boulevard, West Philadelphia.

Firefighters cut a hole in a nearby cyclone fence and shined klieg lights from Ladder 6 on the area.

As in the popular TV show "Bones," Kenneth Lee, an investigator with the medical examiner's office, set out to document the potential crime scene, alternately taking photos and removing layers of debris, before he reached the bones.

Lee recovered a green-checkered dress, red floral blouse, dentures, lilac slippers, a gold locket with photos inside, an identification card with a birth date, a bank receipt, a key and a green carry-all bag - clues that could lead to identification, according to David Quain, forensic-services manager in the medical examiner's office.

But some pieces of the anatomy were still missing, said James McCans, assistant professor of forensic medicine at the Philadelphia College of Osteopathic Medicine, who was asked to bring his cadaver-sniffing dog, "Stache," to the scene.

Stache unearthed a heel bone, a wig, shoes and a woman's watch buried under debris, he said.

Lt. Richard Brown, of Central Detectives, said the arm bone was near the skull in a resting position, as if the deceased had lain down to rest and never got up.

"The bones were very white, as if bleached by the sun," he said. "They were all pretty much intact."

Lee put the clothes and personal items in a brown paper bag, Quain said, and the remains in a black body bag. At 10:35 p.m., he took them to the morgue only a half-block away.

Lee quickly discovered his first lead. The name on an identification card matched the addressee on a letter that was found.

It was: Alice Artison.

But were these her remains?

"You can't be wrong in a job like this," said Quain. "We have had people carrying other people's ID. You notify the family, and find he's alive and, well, he lost his wallet."

Thus, two simultaneous probes were opened: one by investigators who interview the living to help to identify the dead, and the other by an assistant medical examiner, who examines the remains to determine the manner and cause of a person's death.

"We don't want to rush to say anything until we have all the information in," said Quain.

And for good reason: The investigation would take some surprising turns.

It was nearly three years ago when Alice Artison disappeared.

The day before, the retired teacher's aide, then 75, had issued an ultimatum to her husband: If he banished their youngest daughter from their Yorktown home, she'd leave too.

"My dad was at the end of his rope," said daughter Marsha Holley, of the Frankford section. Her sister, Karen, 40, was living with her boyfriend at their parents' house on 13th Street near Oxford, in the same North Philadelphia neighborhood as Mayor Street.

And her father, Leroy B. Artison, now 84, an ex-Marine with 33 years as a Streets Department supervisor, was upset because his daughter's boyfriend woke him up repeatedly with phone calls and coming home late, he told the Daily News at the time.

Karen was the youngest of seven living siblings, a troubled woman in need of mothering, her sister said. "She had mental deficiencies."

Her 4-foot-11 mother tried to protect her, as she did all her daughters. Leroy Artison described his wife and Karen as "Siamese twins."

"Miss Pick," as Artison was known for eating so many pickles as a child, was the kind of mom who'd tuck money in her daughters' hands to help pay bills - when their father wasn't looking.

"It was sad, because so many times, my mom was put in the middle between us and my Dad," Holley said.

Artison had another heartbreaking reason for keeping Karen close. She didn't want to lose another daughter to tragedy.

In 1987, the Artisons had lost a daughter, Sandra, to a maniacal handyman, Harrison "Marty" Graham, who strangled seven victims during sex, abused their corpses and hid them in a room nailed shut in his fetid crack-house apartment.

Sandra Garvin had lived with a boyfriend in the first-floor apartment below Graham, who is serving seven life sentences.

The day before Alice Artison disappeared, her husband had ordered Karen: "Go live with [your] baby's father," according to Holley.

On July 22, 2004, Artison made good on her threat. She disappeared.

The tragic circumstances in Artison's life spurred Detective James Seymour, and later Detective Michael Vincent and Brown, to work nonstop to find her.

"Here was an old lady [who] we thought was met with foul play," said Brown, who at that time was the acting captain of Central Detectives. He dispatched 10 detectives to find her.

Investigators thought it peculiar that Leroy Artison did not report his wife's disappearance for four days. His wife once had filed for a protection-from-abuse order against him, but it had expired. It was the first of what they considered several red flags in the case.

But a confident Leroy Artison told the Daily News at the time that he was certain his wife would return. She always did.

If she was angry about her daughter's eviction, he said, he thought she might stay with her sister, the last person to have seen her. But when she didn't show up after a few days, and none of the relatives had seen her, even he became worried.

"I hope you find my wife, not like you found my daughter," he told Lt. Brown, referring to the death of Sandra. Leroy took a polygraph test and passed.

Detectives interviewed Artison's sisters, daughters, neighbors, friends - even Karen's boyfriend, a parolee with a criminal record.

Detectives checked hospitals and homeless shelters, and talked with street vendors and Progress Plaza merchants. They reviewed surveillance videos outside Alice's favorite stores and checked her bank account, which showed no activity.

To find leads, police and family members offered a reward and posted photos of Alice in neighborhoods and asked newspapers and TV to run stories. Seymour asked homeless advocate Sister Mary Scullion if Project H.O.M.E.'s outreach workers would pass out flyers about Artison as they made their nightly visits to feed the homeless and urge them to come off the street.

After a month, Seymour was stumped. He couldn't understand why Alice had disappeared. She had a family who loved her, and she loved them. Even if she was forgetful, or had a touch of dementia, as one daughter claimed, she was bound to turn up, he said.

It was time for him to turn the case over to Brown and Vincent, of Special Investigations.

In their first week, the detectives obtained search warrants. They got the Police Department's senior K-9 trainer, Paul Bryant, and "Azeem," his celebrated cadaver-sniffing dog, to inspect several houses and parts of Fairmount Park, but nothing turned up.

Then, they retraced each step, and reinterviewed everyone, looking for a clue. They even conducted an analysis of vehicles used by people of interest.

Once, they thought they had found Alice. A woman matching her description was found dead near an Atlantic City casino - but it wasn't her.

Artison's strange disappearance gnawed at Seymour, Brown and Vincent long after they had turned the case over to the Special Victims Unit, a two-person team responsible for finding long-term missing persons.

Though no longer his case, Vincent wouldn't give up. He asked the Artisons to notify him of any leads so he could personally follow up. His file was as thick as a Philadelphia telephone book.

"I was hoping she was still alive," said Vincent. "I was hoping one of her children took her in and didn't tell the rest of the family."

At the monthly review of outstanding cases at Central Detectives, Brown, Vincent or Seymour always asked if there was anything new on Artison.

"Normally, we don't do this, but on this case, we did. Bells were going off," said Seymour.

"She touched our hearts," said Brown.

Years passed. By March 12 of this year, the remains found by the tracks had been logged into the medical examiner's office. That morning, investigator Eugene Supplee recognized the name and called Detective Valerie Miller-Robinson at Special Victims.

"This one really hit close to home," said Miller-Robinson, who operates the missing-person unit with Officer Robert Rajchel.

Supplee and Miller-Robinson knew the daughter of Alice Artison, Marsha Holley, and the heartbreaking story of her mother's disappearance in 2004.

The three had served on an eight-member committee to improve communication among investigators in the medical examiner's office, Police Department and families of missing persons, after a media furor about how a missing person's body had been in the morgue unidentified for a few months in 2005.

"I really wanted to find her mother, but I wanted to find her alive. To be honest, it was a letdown," said Miller-Robinson, referring to Supplee's call.

On the same day, Dr. Gregory McDonald, assistant medical examiner, conducted an inventory of bones just brought in. He first looked for any sign of trauma.

"If someone is shot, or strangled, or stabbed, it may have an effect on the bone. A knife could nick it, or it could be fractured by blunt trauma," said Quain.

The hyoid bone, in front of the neck near the Adam's apple, can fracture if a person is strangled, he added. "You have to look all over because there could be injury all over."

An elderly woman "could have been walking along, fell and fractured her leg. You also have to look at clothing to see if she was shot or stabbed," he said.

If tissue is found on the remains, Quain said, the pathologist will submit it for a toxicology analysis.

But McDonald found no tissue, no broken bones, no suspicious injuries, nothing at all to indicate how she had died, nor whether a crime was committed.

He decided to send a specimen to the FBI's DNA lab to be analyzed. Meanwhile, McDonald asked for the opinions of two top forensic specialists:

Dr. Haskell Askin, a renowned forensic dentist, or odontologist, helped identify victims of Hurricane Katrina and of the World Trade Center after 9/11.

In 1998, he wowed investigators here when he identified the decapitated remains of Maria Cabuenos through bite marks on her notorious killer, Arthur Bomar. He's been a consultant with the Philadelphia medical examiner's office for 35 years.

Arthur Washburn is one of only 40 active forensic anthropologists in the U.S. and one of a few in the area. He knows bones: He can pinpoint the sex, age, ancestry, stature and kind of bones with surprising accuracy. He teaches anatomy to medical students and others at Temple University and has been working with the Medical Examiner's Office for more than 16 years.

Marsha Holley, like the rest of her family, was devastated when her mother disappeared.

"I was the one she delegated things to do. She always trusted me to do that for her. I felt it was totally on me" to find out what happened, she said.

Holley kept in touch with every police detective and with investigators in the medical examiner's office.

She was so well-known and cared so much that she was asked to join the special eight-member committee to address how the city should handle missing persons.

"We brainstorm about how we can do a better job," she said, after attending two committee meetings.

Of the four citizens on the committee, three had family members who had been missing, two of whom were later found dead. Only Alice Artison was still missing.

The committee was working. Communication is improving, said Quain. Two police officers and two investigators from the medical examiner's office now talk at least once a week, if not daily.

Often, remains will stay unidentified in the medical examiner's office if a family has not reported the person missing. Since 2003, there have been 13 such cases.

During Artison's disappearance, Holley said, she became close to Miller-Robinson, who investigates long-term missing persons, and checks whether they are unidentified in the medical examiner's office.

Miller-Robinson advised Holley of the national recommendation for such families: Donate a DNA specimen to the FBI's DNA laboratory in Quantico, Va.

If Holley's mother was found, the detective told her, technicians could compare their mitochondrial DNA, which is passed down only through females in a family.

In early 2006, Holley and a sister submitted DNA specimens to the FBI database.

Now, their donations seem prescient.

Normally, the forensic dentist examines the mouth of the skull, looking for fillings, crowns, missing or crooked teeth, and whether such teeth sit high or low inside.

Askin always takes two sets of X-rays of the teeth or gums of an unidentified corpse: one set for the ME's Office and one for his home office - so he can see the X-ray while discussing it.

"Sometimes there are features in the bone [such as] cysts, retained roots, teeth broken off, or impacted, or a root canal," he said. "Sometimes baby teeth never came down. Is there a space between the front teeth?

"If there are no longer teeth, we have the shape of the gums. The bones are the shape of the jaw."

Odontologists look for a clue in the dentures. In some dentures, a tissue-paper label with the name of the wearer is embedded in a channel and covered in plastic.

"That's what we look for first," said Askin, who years earlier had identified Artison's daughter. But no label was found in the dentures.

If no dental records, plaster casts or X-rays are available - as in this case - the dentures or partial denture still must fit into the jaw, he said.

When he put the dentures into the jaw of the skull, they fit perfectly. In fact, the jaw bone had grown around the dentures to accommodate them, an indication they had not fit properly.

Without question, he said, the dentures belonged to the woman whose remains were found.

"This is really a team effort, and why we have these consultants, like [me] and Dr. Washburn," said Askin. "We are looking for consistency" in identification.

While the odontologist examines the teeth and upper and lower jaws, the forensic anthropologist examines bones of the body, in particular, the skull and the size and shape of the pelvis, which can reveal gender. The pelvis is wider in women than in men to accommodate childbirth.

Washburn, an expert in determining age, stature, sex and race, could immediately tell that the pelvis on the examining table was that of a woman.

Based on arthritis and age-related changes to some of the bones, he could say that she was age 60 or older.

"I usually say, 'I don't want to know if it's a male or female, black or white,' before I do my analysis," said Washburn. "I don't want that knowledge to influence my analysis. It's a mystery. Skeletons tell a story."

This time, however, he knew that investigators suspected the remains belonged to an elderly African-American woman. But McDonald wanted the anthropologist to independently confirm the identification.

Washburn then took a series of measurements of each bone, and input more than 75 measurements into a computer program developed at the University of Tennessee forensic-anthropology center.

Within seconds, the computer compared his measurements to more than 2,100 other skeletal remains in the database and generated a surprising profile.

The bones appeared to be from a white woman, an atypical reading, he said.

At first, he thought, "This was not who they thought it was," but, then he recalled a similar case a few years ago when he contacted Dr. Stephen Ousley, who co-developed the computer program at the University of Tennessee.

In that case, he asked Ousley, now at the Smithsonian, to input the measurements in a newer version of the computer program. Both anthropologists came to the same conclusion: the deceased was of mixed race.

Washburn's visual exam of the elderly woman's remains - particularly, the opening for her nose - indicated she was probably African-American.

"Ancestry or race are more difficult to determine. I'm very cautious," he said. "When you say someone is African-American, what we don't know is how mixed their ancestry might be."

About this time, he added, Supplee had spoken with Artison's daughter, who reported that her mother had "a lot of Native American ancestry."

Although cases are added annually, Washburn knew the database didn't have as many skeletal measurements of Native Americans as of whites and African-Americans.

"This woman was thought to be African-American, but she had Native American ancestry," he said.

The mixed-race finding, though surprising, was consistent with other information gathered so far: The remains appeared to be that of Alice Artison.

Last month, Miller-Robinson took the belongings in the brown paper bag to Artison family members to identify.

The key fit in Alice Artison's front door. The gold locket contained photos of her granddaughter and great-granddaughter. The green-checkered dress was the style she wore. They were her lilac slippers.

"We have all these things that say it's her, and nothing that says it's not her," said Quain. "We're 99.9 percent sure, and the DNA will take us to 100 percent.

There was only one problem: It could take another six to eight months to make a positive identification, due to a DNA backlog at the FBI lab.

The Artison family decided to wait for the DNA results.

"I have a mixed reaction," said Artison's husband, Leroy. "It is mystifying, if it is her, how [the remains could] go unseen for so long.

"She doesn't have relatives in the area, and there's no reason to be there." Yet, he added, "Some of the things brought here were compelling.

"I don't want to believe it is her," he added.