Michael Nicholaou slipped into the West Tampa home on New Year?s Eve. It was daylight. He wore a black suit and tie and carried a guitar case full of guns.

He found his estranged wife at the dining room table.

"You didn?t think you were ever going to see me again," he said.

When it was over that day on Walnut Street, blood stained a floral bedspread and a beige and pink dresser. Nicholaou, 56, killed his wife and fatally wounded his stepdaughter before shooting himself in the mouth.

The new year would ring. The crime scene tape would come down.

But the name Michael Nicholaou would find its way north into a mystery two decades old, a string of unsolved murders that gripped Vermont and New Hampshire.

A St. Petersburg private investigator, a retired Vermont criminal profiler and a New Hampshire cold case detective would piece together a killer?s past.

They would learn Nicholaou was a war-scarred veteran with a missing girlfriend and a dead wife; a former porn shop owner who both charmed and terrified women; a man who lit fires in anger and was always on the run.

Was he also a serial killer?

Lynn-Marie Carty sniffled with a sinus infection on New Year?s Day. She sat on the couch in her St. Petersburg home in her bathrobe with the morning paper. The 2005 Christmas season had been busy for Carty, 49, who makes a living reuniting families.

When she opened the paper to the story about the Tampa murder-suicide, the name jumped off the page.

It was him.

Her only brush with Michael Nicholaou (pronounced NICK-allow) had been a phone call five years earlier. Carty was hired by a Vermont mother to find a daughter, Michelle Ashley, who had two babies with Nicholaou before she disappeared in 1988. Rose Young begged Massachusetts police for help, but they never found Michelle.

The mother suspected Nicholaou, based on something her daughter once said:

This wasn?t the sort of case Carty had in mind when she founded ReunitePeople.com in 2001. She liked happy endings. Clients sent her butter?fly trinkets, symbolizing the new beginnings she made possible.

Carty knew about second chances. She had her first child at 16 and left her home in Massachusetts. She wound up in St. Petersburg with two kids, living in a motel and driving a $150 car with a broken windshield.

Carty was working at a day care in 1995 when a friend told her about baby graves dug up in Royal Palm Cemetery to make way for construction. She tracked down the babies? families and persuaded a Clearwater lawyer to hire her as a full-time investigator. The class-action lawsuit made the papers, and Carty was on her way to becoming a private detective.

She loved the work. She liked piecing together human puzzles and sorting through documents. Her son, Jason Heath, taught her to use the Internet and became an investigator, too.

Before long, she was charging people $2,100 to find a missing relative.

It took her 15 minutes at the computer in 2001 to track down a phone number for Michael Nicholaou.

Carty asked about Michelle. He denied knowing her, but Carty pressed on.

Carty asked about the children, Nick and Joy. He had them, he said. They were fine. The conversation was short, and when Carty called back the next day, Nicholaou?s phone was disconnected.

She hadn?t thought much about him since, but that New Year?s Day, there he was in the headlines: Marital dispute ends in deaths. He had killed his latest wife and her daughter.

What about Nick and Joy, now teenagers? Who would take care of Michelle?s kids?

Carty tracked down Nick Nicholaou the next day on the phone and told him she didn?t think their mother had abandoned them. He and his sister had always thought otherwise. Nick cried as he described their hard life, being dragged around by a father still traumatized by Vietnam.

Carty vowed to reunite Nick with his mother?s family, a gift for his 18th birthday.

But the woman with the butterfly business card holder couldn?t stop wondering about Michelle.

Growing up in the Connecticut River Valley, Michelle Marie Ashley was a tomboy who built tree forts with her cousin in the thick woods. Later came fashion and men.

She met one and ran away with him. The next time family saw Michelle, in 1984, she had a baby she turned over to the father. It wasn?t long before she had met another man, her mother?s age, and was pregnant again.

That man was Nicholaou.

He had a deep voice and a thick New York accent. Michelle told family they were married, though it couldn?t be confirmed through public records.

She gave birth to Joy in August 1986 and Nick in January 1988, keeping detailed notes in their baby books.

Her family thought Nicholaou was creepy from the beginning, too quiet during his visits to Vermont, where Michelle?s mother and grandmother lived. He and Michelle had an apartment in Holyoke, Mass., about 110 miles down Interstate 91. The two were always in the car. Connecticut. Virginia. Louisiana. Massachusetts.

He wouldn?t let Michelle shave her underarms, according to Chicki Merrill, her aunt. Nicholaou seemed to follow Michelle everywhere. At times she acted as if she wanted to confide in her family, but Nicholaou was always on her heels, cousin Julie Virgin said.

Michelle had been good about writing to Virgin, dropping baby pictures in the envelope, but her letters slowed.

Finally, she told her mother: She feared Nicholaou. She planned to leave him after her sister?s November 1988 wedding.

In December 1988, her mother walked into the couple?s Holyoke apartment, looking for Michelle. The Christmas tree was up, presents unopened. The refrigerator was full, food spoiled.

Michelle?s baby books had been left behind, incomplete.

In the years that followed, Nicholaou, with kids in tow, would visit his mother in Virginia, his friends in Florida and Army buddies across the country. When people asked about Michelle, he told some that she had run off with a drug dealer. He told others she was dead.

It was days after Carty first read of Nicholaou?s Tampa rampage.

With Michelle in mind, she punched words into Google.com: New England. 1988. Murder.

She clicked on the story of a pregnant New Hampshire woman who was the sole survivor of a series of attacks known as the Connecticut River Valley murders.

The remains of at least six other young women had been dumped beside back roads along I-91 in a stretch that straddled Vermont and New Hampshire. A killer had slit throats and stabbed victims repeatedly in the lower abdomen, leaving some of them fully clothed.

There was Mary Elizabeth Critchley, the hitchhiker. Bernice Courtemanche, the 17-year-old nurse?s aide. Ellen Fried, the nurse. Eva Morse, the single mother. Lynda Moore, the housewife. Barbara Agnew, another nurse. And Jane Boroski, the pregnant woman who survived.

Carty, who wouldn?t even let her kids watch horror movies, felt drawn into a serial murder investigation.

She noticed right away that several victims were nurses. She remembered hearing that Nicholaou?s first wife was a nurse and that his mother worked at a hospital.

She read that the killer knew the area.

Michelle?s family lived in the heart of the Connecticut River Valley. One woman?s body was found near their town, and Claremont, N.H., setting for several of the slayings, was between there and Holyoke, just off I-91.

The killer used a martial arts grip on the surviving woman. Nicholaou had a black belt in karate.

What Carty found most curious was that the last attack was only four months before Michelle ? and Nicholaou ? disappeared from the area.

Carty read online about John Philpin, a criminal psychologist who, in the 1980s, helped police profile the serial killer.

She called Philpin in Felchville, Vt., and told him what she knew about Nicholaou, hoping he would take her suspicions to police.

Carty had heard about DNA testing. Couldn?t someone check samples from Nicholaou?

Philpin wanted more information. So did Carty. She rush-ordered a book from Amazon.com about the murders: The Shadow of Death, by Philip E. Ginsburg. The book explored 11 deaths, but police thought only some were related.

Carty read it in bed, skipping over the bloody parts. She left it in another room at night so she could feel safe.

The book never mentioned Nicholaou. But in her mind, he became its main character.

One of the Connecticut River Valley victims was Ellen Fried, supervising nurse at Valley Regional Hospital in Claremont, N.H.

Before the age of cell phones, 26-year-old Fried would use a public phone at Leo?s Market to catch up with her out-of-town sister, usually at night after work. Leo?s was on Main Street, a straight shot from I-91.

Their last conversation was recreated in The Shadow of Death.

For almost an hour on July 20, 1984, the two talked. Then, something spooked Fried.

The sister heard an engine turn over. When Fried returned to the phone, she said she wanted to make sure her car would start. They talked for a few minutes, then hung up.

Fried was the third woman to disappear. The police began to suspect they were dealing with a serial killer with a penchant for nurses.

Fear crept into Claremont. Security guards shuttled nurses to their cars. Boyfriends armed girlfriends with guns. People locked their doors.

Claremont hasn?t changed much from those days. Roadside signs say "Moose Crossing" and advertise maple syrup. Paper mills loom large and empty. And the conversation is seldom far from the fear that took the town 20 years ago.

"It was the worst thing that ever happened in this area," said Carla Hawkins, sitting on a stool at McGee?s, one of the town?s two bars. Her family took in one of the victim?s daughters.

"I was freaked out about it," she said. "Still am."

Most everybody knows about the book. Librarians keep four copies at the Fiske Free Library, behind the counter to discourage theft. Inside the book are details that colored rumors at the time, stories of an elusive man who left police few clues.

The one people remember is that someone kept calling local radio stations back then, obsessively requesting Bad to the Bone.

It was a wildly popular song in the 1980s, all over MTV. It was Michael Nicholaou?s favorite song.

Carty tracked down a phone number for Susan Nicholaou, the Connecticut nurse Nicholaou married in 1978, before he hooked up with Michelle. The two divorced in 1982, a year after the first valley victim, Critchley, disappeared off of I-91 in Massachusetts and later turned up in New Hampshire.

Though little is known of the short marriage, Nicholaou took off with their daughter soon after she was born, infuriating his wife, according to relatives.

If Nicholaou was involved, maybe Susan Nicholaou suspected something, Carty reasoned.

Carty called.

She remembers the ex-wife?s response and the way her voice shook on the phone.

Carty pressed on. What kind of cars did he drive? Susan said she barely saw him.

Had she been afraid of Nicholaou? Carty says Susan screamed the answer:

The conversation was over.

Susan Nicholaou declined to speak with the St. Petersburg Times.

Nicholaou?s own mother denied knowing him until she learned that her name and phone number were noted in a Tampa Police Department homicide report. It was about Nicholaou?s December suicide and the shooting deaths of Aileen Nicholaou and her daughter Terrin Bowman. He and Aileen had met through a newspaper personal ad before melding their families in the late 1990s.

"I threw him out years ago," his mother, JoAnn Sobotincic, told the Times. "He stole my car and took off. I haven?t seen him or heard from him since."

Nicholaou had told his wife Aileen that his mother molested him when he was young. Sobotincic said Nicholaou was never sexually abused, but that her husband, Rudy, hit him. His birth father, Edward Stafford, is a registered sex offender in South Carolina. His mother divorced Stafford on grounds of "extreme cruelty" when Nicholaou was 3 years old, records show. She told the Times Stafford was a child molester.

Nicholaou rode a motorcycle to high school in Farmingdale, N.Y., where he was a wrestler. He enlisted in the Army in 1968, in Brooklyn.

In Vietnam, he flew helicopters for the 335th Aviation Company, called the Cowboys. Interviews with a dozen Cowboys reveal a brave and duty-bound man with a dark side. He earned a Distinguished Flying Cross, Bronze Star and Air Medal, among other honors, flying into hot zones to drop supplies and recover the wounded.

But at least once he left camp on his own, carrying only a knife and seeking hand-to-hand combat with the enemy. It became a legend in the company.

In May 1971, the government charged Nicholaou and seven other helicopter crewmen with murder for strafing innocent civilians while on a flight in the Mekong Delta the year before. The military dropped the charges because of insufficient evidence, according to news accounts from the time.

Days after the charges were dropped, Nicholaou was released from active duty. When he returned to the United States, his homecoming celebration was short.

He worked odd jobs and moved from place to place, never staying anywhere for long.

Friends began to notice evidence of posttraumatic stress disorder, a mental illness for which he later sought treatment in Miami and Tampa.

His mother said she heard little from Nicholaou. But FBI agents have contacted her three times in the past 15 years looking for him, she said. Once, they asked about Susan Nicholaou?s baby. The other times, they didn?t say why they wanted him.

By 1977, he was living off and on in Virginia. Police in Charlottesville busted him for dealing drugs and used him as an informant, according to former Chief John Bowen.

For years afterward, Nicholaou told people he was cop, or that he worked for the CIA.

He opened a porn shop called the Pleasure Chest in Charlottesville in 1983, a year after his divorce from Susan. He was living with his business partner and the partner?s wife. Nicholaou would leave town alone sometimes, later telling friends he had gone to New York or Miami.

Two weeks after the porn shop opened, Nicholaou and his partner were charged with selling obscene materials. A jury convicted them. Months later, police raided again. This time another jury returned a not guilty verdict.

Nicholaou talked to the local newspaper, the Progress.

"Evidently the police don?t have enough serious robberies, murders and rapes to occupy their time," he said in a story published May 22, 1984.

Eight days later, 600 miles away, Bernice Courtemanche set off hitchhiking in Claremont, looking for a ride east to Newport, where she planned to meet her boyfriend. She wasn?t far from Leo?s Market when she left.

She never showed up.

Carty jotted a note on a copy of a 22-year-old news clipping from the Progress, circling Nicholaou?s quote.

"Look what Nicholaou had to say about the murder and the police," Carty wrote.

In her mind, his time in Virginia was no alibi. By all accounts, Nicholaou had plenty of reasons to drive north. He was in Vermont over Christmas some years, and his ex-wife Susan lived in Connecticut.

The butterflies on Carty?s shelves made way for her growing collection of The Shadow of Death copies. By spring, she would own 11, thinking they might become valuable one day. Early on, her dog tried to drag the first copy outside. He knows it?s evil, she thought.

She spent thousands of dollars searching records.

She asked strangers to compare a composite sketch of the valley killer with a photograph of Nicholaou, pointing out the dark-framed glasses that both men wore.

Day and night, she sent e-mails to Michelle?s family members, asking questions they couldn?t answer. At first they were helpful, but gradually they questioned her persistence.

Carty felt she had no choice.

How could she ignore the clues?

There was the note in Michelle?s abandoned baby book that placed her and Nicholaou in a Hanover, N.H., hospital on Thanksgiving, 1986. A nurse from the same hospital disappeared in January 1987, miles from the Vermont home where the Nicholaous spent Christmas and the weeks that followed.

And what about his car? Relatives remember, in the mid 1980s, taking Christmas gifts out of a station wagon with wood-paneled sides. The surviving victim had told police her attacker drove a wood-paneled Jeep Wagoneer.

Carty felt guided by the spirit of Michelle?s mother, who had died without answers to her daughter?s disappearance. Carty had often yearned for a better relationship with her own mother. She resolved to finish the job she started.

It had been a month since Carty had first spoken to crime profiler Philpin.

He was saying all the right things. The man who had helped police on hundreds of homicides, including the Gainesville student murders of 1990, agreed that Nicholaou could be the killer.

"This is the first, I?d call it major, lead in three or four years," Philpin later told the Times.

Carty didn?t understand what was taking so long. It was February. Nicholaou was dead but families deserved answers.

She felt there must be DNA evidence from the woman who survived the attack.

Again, she wondered: Couldn?t someone test Nicholaou?s DNA?

She dialed the New Hampshire State Police.

At least once a week, a tie-wearing detective named Steve Rowland climbs a narrow wooden staircase into the past. He riffles through thick volumes of murder files in the third-floor cold case morgue of the major crimes unit in Concord, N.H.

Back at Rowland?s desk, a bulletin board posts the faces of women killed decades ago, their deaths never solved.

It had been six months since someone had called about the valley murders. Rowland usually hears from family members seeking updates, or people who want to share theories about the killer. But Lynn-Marie Carty had more.

Carty rattled off what she knew, keeping Rowland on the phone for half an hour. It was the first time Rowland had heard of Michael Nicholaou. Carty answered Rowland?s questions before he asked them. She told him of the matching cars and Nicholaou?s links to the area. When he asked for more, she mailed him a timeline and news clips.

Her tip revived the investigation.

By April, authorities considered Nicholaou one of their three strongest suspects, Rowland said.

The other two suspects are still alive. Police can?t check their DNA without probable cause. That?s not the case with Nicholaou.

"His profile fits the profile of somebody that would commit this type of crime," Rowland said. "There?s no question about that."

He has been a cop too long to get his hopes up.

But he was intrigued by Nicholaou?s rocky childhood, his war trauma, his capacity for violence and his issues with women. And Nicholaou had traveled into the Connecticut River Valley area during the time of the murders.

And so Rowland agreed.

He would have someone compare Nicholaou?s DNA with DNA gathered during investigation of the serial killings.

Rowland now has Nicholaou?s fingerprints from Tampa police, and he?s trying to get DNA from the Hillsborough County Medical Examiner?s Office. He plans in the next few weeks to compare the fingerprints with some gathered from Boroski?s car.

It will be up to the forensics lab to test the DNA, but the lab is backed up with current homicide cases, Rowland said.

On average, Carty e-mails Rowland seven times per week, asking him to hurry the process along, he said in April.

Rowland said he doesn?t expect an answer until late in the summer, but he has already dug through physical evidence from three of the old cases, and he thinks that the killer must have left his DNA behind.

He wouldn?t be surprised if the killer was Nicholaou.

Carty grows antsy, waiting. Between paying jobs, she scours the Internet for unidentified murder victims who might fit Michelle?s description. She digs through other cold cases, including several deaths in Texas, another in Massachusetts.

Nothing moves fast enough for her.

She thinks about calling America?s Most Wanted or Dr. Phil. By June, she has convinced a 48 Hours producer to fly to Florida to hear her out.

Michelle?s sister, Tammy Patla, doesn?t talk to Carty anymore. Patla blames Carty for jeopardizing her relationship with Nicholaou?s children. Carty?s claims upset Nick.

"I don?t deserve this," says Nick Nicholaou, 18. "I don?t know what this lady?s talking about."

The private investigator still trades e-mails with Jane Boroski, the surviving victim from New Hampshire, who encourages her efforts but, like Rowland, hesitates to be too optimistic. Boroski looked at a recent photo of Nicholaou and couldn?t say whether he was her attacker all those years ago.

Carty won?t entertain the idea that the DNA might not match. She still has no solid answers, but the killer?s shadow creeps into her nightmares.

In them, she?s alone in the dark, outside Leo?s Market in Claremont, talking on a pay phone.

Times researchers Cathy Wos and Carolyn Edds contributed to this report.