It was edging toward midnight, and the detective, Bernard Forsythe, finally thought he was getting somewhere. In this concrete blockhouse of a police station, the 58-year-old businessman seated before him in the tiny office had kept calm through more than an hour of persistent questioning. But now his composure seemed to be wavering.

"It's obvious you're upset at this point," said Forsythe. Leaning close, he feigned a note of empathy. "I understand that."

The two men sat in shirt sleeves, facing each other in front of a gray metal desk. The office door, shut behind them, muffled any sounds from the adjoining squad room, where the weekend night-shift detectives of Montgomery County's Rockville police district were at work.

It was 1988, the middle of August.

"I know you're tired," Forsythe continued. "You've been very gracious. I'm going to ask you one or two more questions."

In the fluorescent light, he studied the man's face, the way cops do, looking for some glimmer of admission.

"Did you kill your wife?"

Gregory Tu's face showed nothing.

The question, blunt as it was, should not have surprised Tu. Though not married, he and Lisa Tu had lived as husband and wife for about a decade, in a red brick Colonial shaded by pines in Potomac. But now Lisa, 42, was nowhere to be found, having vanished exactly a month before. And from every question this homicide sergeant had put to him over the last hour, it was obvious what the police believed: that Gregory, in some calculated fashion, had made her disappear.

They believed it then, they believe it today. Nearly four years after Lisa Tu vanished, after the most oddly tortuous investigation any Montgomery detective can remember, Gregory Tu goes on trial today for the second time, accused of carrying out an elaborate murder-and-coverup scheme. He has denied the charges from the outset. No one heard a shot; there's no corpse, no weapon, not a single eyewitness -- just a painstakingly built theory of what happened, and why, in the furnished basement of a $360,000 home on Deep Spring Drive.

On this night in August, however, as Forsythe confronted Tu for the first time, Lisa's month-long absence had been under police scrutiny for only three days. And Gregory, who sat in a veil of cigarette smoke, his dark hair combed back above a drawn expression, was a stranger.

Forty years removed from Shanghai, a lover of classical music and fine cooking, he considered himself a man of culture. Socially polished, a graduate of the University of Southern California, he was a product of China's pre-communist intellectual class, a Washington area restaurateur who once managed Trader Vic's and more recently had turned to the real estate business. Barely a trace of accent remained in his voice.

"How can I kill my wife?" he protested. "I love her so much."

"It happens," Forsythe said. "Whether it was an accident, the heat of passion, you find out she's having an affair. It happens."

"She does not have an affair," Tu insisted.

In fact, she had, for more than a year, with a restaurant captain in Falls Church who told police of the liaison. And that wasn't the only wrinkle in the case that bothered Forsythe; he and Tu already had gone over some of the others: Why was $44,000 missing from one of Lisa's bank accounts? Whose idea was it to buy the $200,000 accidental-death policy? Why did Gregory buy a pistol, a Browning 380 semiautomatic, then dispose of it? To whom did Gregory owe thousands of dollars, and for what? And why, within days of Lisa's disappearance, did he suddenly get rid of her favorite sofa, the one in the basement, where she liked to sleep on warm evenings?

He wasn't under arrest yet -- that came weeks later, followed by a long trial, a guilty verdict and a life sentence. And at every turn, he argued that he was innocent.

In a letter to the judge in the case, one of Lisa's sisters wrote of the importance in her Buddhist faith of "a final and proper ceremony" for the dead, and of her lasting anguish at not being able to provide one; she wrote of her dreams about Lisa, of seeing her sister dismembered, and awakening from "these nightmares all soaked and crying." The judge, hoping to end this "psychological horror," suggested he'd lighten Tu's sentence if only Tu would point the way to Lisa's remains.

Instead, Tu appealed his conviction, claiming that police had overstepped the bounds of a search warrant. And he won a new trial.

Today, as the trial begins, he's as adamant as he was four years ago, the night a telephone call first summoned him to the cramped quarters of the Rockville Investigative Section.

"You're saying you did not kill your wife?"

"No, sir."

Forsythe stared at him.

"Not accidentally?"

"No, sir."

The Last Time About a mile west of Route 270, just beyond Rockville, the neighborhood of Potomac Commons stretches comfortably over dozens of acres, its 10- and 12-room homes set back amid stands of pines, its roads and cul-de-sacs adorned with maple trees and Bradford pears.

Shortly after 1:30 in the morning on July 13, 1988, Loretta Hum, a close friend of Lisa Tu's, guided her big Pontiac Parisienne past the ball field and swung left into the driveway of a corner Colonial on Deep Spring Drive.

She and Lisa had played mah-jongg all evening with friends, and Lisa, on the ride home from Arlington, had been her garrulous self. "She was laughing a lot, she talked a lot," Hum later told a jury. "Sometimes she hummed some Chinese song."

Now, with $415 in winnings tucked in her purse, she stepped from Hum's car and walked in its headlights toward the door.

"She was a very open person, and always very good to her family," one of her friends recalled. Like others, this friend also remembered her as "a simple person, naive. Her world was material things, where to shop, where to go eat. She wasn't a greedy person; she was very giving. She just wanted to enjoy life. That was her way."

"Extremely beautiful and somewhat pampered," is how one investigator described Lisa Tu. "She was used to being taken care of."

As friends tell it, she came from a modest beginning. The second of four sisters, she grew up in Taiwan after her mother, a domestic, and her father, a member of China's nationalist military, fled the Communist mainland with Chiang Kai-shek in 1949. Her lifestyle changed dramatically, however, when as a young woman she began an intimate relationship with a wealthy Hong Kong businessman named Wing Lau.

By the time they separated and Lisa moved to the Washington area in the 1970s, she had two children, Kai Lau and Sophia Lau.

Those years with Wing Lau left her financially settled, friends said. When detectives looked in her safe-deposit box after she disappeared, for instance, they found jewelry worth "tens of thousands of dollars, and probably more," an investigator said. She also lent at least $50,000 to a nephew of Gregory's. Lau, meanwhile, continued to wire her $5,000 a month for living expenses, and set up a college fund for their son, depositing more than $44,000 in Chevy Chase Bank, with Lisa as custodian.

Lisa's car, her BMW, was parked in the garage that early July morning, as Loretta Hum watched her open the side door to the house.

Hum saw nothing unusual. On the left side of the driveway, a year-old Camaro was parked in its normal spot, which meant Gregory was home. The only other person in the house, Hum knew, would be Gregory's mother, who was 93, and whose hearing and short-term memory were all but gone. At this hour, she'd likely be fast asleep on the second floor.

The rest of the family was away. Lisa's son, Kai, who would soon turn 19, was on a vacation in Taiwan, a high school graduation gift. And just the day before, Lisa had put her elderly mother and 12-year-old daughter, Sophia, on a flight to California, where they planned to visit for a month with one of Lisa's younger sisters, Linda Chung.

Before she flicked off the Pontiac's high beams and backed out of the driveway, Hum told the jury, "I saw her walk in and lock the door. ... Then she turned out the light."

And that was the last time Hum saw Lisa Tu.

The man who saw Lisa next -- the man she considered her husband -- was having a hard time coping in the twilight of middle age. Things had not gone well for Gregory Mung-Sen Tu in recent years.

He too had fled the Communists, when his parents, both university educators, sent him abroad amid civil war in the late 1940s. Although he studied geology at Southern Cal and earned a degree in 1954, his real love, it turned out, was running restaurants. He found a future in the Trader Vic's chain. By 1961, the year he married Setsuko Tu, his first wife, he was a supervisor of East Coast operations and general manager of Trader Vic's in the Capital Hilton, two blocks from the White House.

With help from partners, he opened a restaurant of his own in 1969, the Pagoda 7 in Hillcrest Heights. And three years later, he opened another, the Orchid 7-Bethesda. It was all a prelude to his most ambitious venture. With $500,000 spent on start-up costs, and with hand-crafted decor gathered from across the South Seas, Gregory Tu's Orchid 7-Georgetown held its gala opening in the Foundry Building in July 1977.

A woman named Lisa, who had been in America only a few years, and who liked to keep busy, took a job there as a hostess.

She couldn't help noticing the owner, and it wasn't long before their romance began.

Setsuko Tu recalled that her husband of 16 years came home one evening in 1977, surprised her with the news that their marriage was over, then packed his suitcases and walked out the next day.

It was lucky for her she got the Pagoda 7 in the divorce, because Gregory's other two restaurants eventually went under, leaving him tangled in a thicket of lawsuits. He and Lisa were barely settled in their new home in 1979 when, as a legal precaution, he transferred ownership to her name alone. However nice their life together had been early on, several of Lisa's friends and relatives testified, things began to change.

The former grand host at Trader Vic's and the Orchid 7s joined the General Development Corp., which, among other things, sold Florida house lots to immigrants and foreigners. As a broker working on commission, he traveled extensively in the Far East, yet closed only enough deals to earn $12,000 in 1987, company records show. Six months into 1988, his net income was less than nothing -- he owed the company about $1,800 for advance commissions on sales that never went through.

General Development eventually pleaded guilty to criminal fraud charges and agreed in bankruptcy court to refund $160 million to its customers. But that was long after July 13, 1988, the morning Lisa came home smiling from her mah-jongg game and locked the door behind her.

Minutes after turning off the outside light, she went to a telephone somewhere in the house and dialed a number she knew by heart. The man who answered, Martin Liu, then 43, had just got home himself, after a late shift at the Peking Gourmet in Falls Church, where he was a captain of waiters.

Gregory later insisted to police that Martin Liu was merely a mah-jongg friend of Lisa's. But for 18 months before her disappearance, Liu testified, he and Lisa were lovers as well.

Some of those closest to Lisa, including her sister Linda Chung, said they knew or sensed she was having an affair. Chung also recalled that Lisa spoke of having frequent loud arguments with Gregory, usually about money. The house and almost everything in it legally belonged to Lisa, and "she was talking about kicking him out," Chung testified.

Liu added, "She told me that she doesn't want Gregory to touch her anymore." As for their telephone chat that early morning, Liu told the jury, it lasted only a few minutes. Then they said good night.

"Do you remember whether or not you told her that you loved her during the course of that conversation?" a prosecutor asked.

"I think we say that, yes."

That was the last time he heard Lisa's voice.

A Sudden Trip There's a void in the Lisa Tu case that police believe only one person can fill. Although Gregory Tu chose not to testify at his trial and has declined to be interviewed, he spoke at length with police before and after his arrest. According to detectives' notes and transcripts of the interrogations, here's what he said:

He and Lisa had an "excellent" relationship and "were always very truthful to each other." He must have been dozing when she arrived home that morning, because he didn't hear the door open. But he did wake up when she padded into their bedroom upstairs and kissed him lightly.

"We made love," he said.

Then he slept until long after daybreak.

When he awoke, Lisa was beside him, still asleep. Ordinarily in such hot weather she might have slept in the finished basement; the air was cooler there, and she liked the sofa. But recently they had noticed signs that mice were nesting in the couch. Lisa was horrified, almost hysterical, and wanted him to get rid of the sofa as soon as he could.

He spent most of Wednesday the 13th at his office.

About 9 that night, over dinner, Lisa announced that Eve Wang, a longtime friend of hers, had called from San Francisco. Wang, who owned a restaurant, was scheduled to have surgery, and wanted to know if Lisa could visit for a couple of weeks, to help run the dining room.

He drove her to Dulles International Airport the next afternoon, Thursday, July 14. He paid cash for a ticket at the United Airlines counter and handed Lisa's only suitcase to a baggage check-in clerk. Then he kissed her goodbye and watched her board a 5 p.m. flight to Los Angeles, where she'd have to change planes for the second leg of her trip.

She called him twice after that, once during her stopover and again a few days later from San Francisco. She said she hoped to be home by Monday, July 25. In the meantime, no one in the family was to bother her with calls; she'd be too busy in the restaurant.

Not until days later, when she failed to return home, did he realize that Lisa had lied to him about Eve Wang. He could only surmise now that Lisa had some secret reason for going to California, a reason so deeply personal that she invented a cover story. Apparently something awful had happened to her along the way; maybe she was abducted or suffered amnesia. But it wasn't his fault. All he did was put her on the plane.

The transcripts of Tu's interviews show variations in his story as he told it again and again, some of them small, some not so small.

But this part hasn't changed: "I never lifted a single finger to my wife. I love her very much and I know she loves me. Just thinking of her death is offensive to me, much less killing her."

A Clue in Playboy In the days after July 14, 1988, whenever friends of Lisa's happened to call, Gregory explained about her sudden departure for San Francisco. It wasn't long before word of the trip reached Lisa's 79-year-old mother and young daughter, who were settling in for a month's visit with Linda Chung in Fullerton, Calif.

It wasn't long, either, before one of Lisa's friends disobeyed her supposed instructions and tried to call her at Eve Wang's restaurant, only to find out that Wang was in good health and hadn't seen Lisa for months. This news also spread quickly to Linda Chung's house.

At first, it caused only annoyance, Chung said in an interview. She and others assumed that Lisa, after packing off her mother and daughter, was somewhere in a tryst with Martin Liu. Although Gregory had watched her board a plane, maybe she got off before it left. Because no one wanted to betray Lisa's secret, no one confronted Gregory with the truth about San Francisco. And for weeks, no one notified the police.

Yet family suspicion built.

Lisa's mother, who testified that she knew of nothing wrong with the sofa, said she started worrying when a friend told her that Gregory had thrown it out on Saturday, July 16. It wound up pulverized in a landfill.

After July 25 passed and Lisa still hadn't come home, the family worried even more. Then Kai, Lisa's son, returned from Taiwan, stopping as planned at Linda Chung's house on Aug. 3. Lisa had marked the date on her kitchen calendar weeks ago. Wouldn't she at least have called?

All along, Martin Liu kept insisting to Lisa's closest friends that he knew nothing of her whereabouts, that she wasn't secretly lounging in his apartment. Finally they believed him, and faced their worst fear. On Aug. 10, Lisa's mother and Kai flew back from California and reported her missing to the Montgomery County police.

Then they went home and looked around.

Gregory was in the Far East and wouldn't be returning for three more days. In Gregory's den, Kai testified, he opened a bank statement and saw that on July 8, the week before his mother disappeared, someone withdrew $44,000 from his college fund.

He said he was even more frightened by what he didn't find in the den: Gregory's gun, the Browning 380, was missing from a drawer.

Linda Chung and another of Lisa's sisters arrived from the West Coast the next night, and the search of the house went on. Though several of Lisa's favorite dresses were gone, as well as one suitcase, Chung said in an interview, she found several personal items that her sister rarely traveled without.

Gregory returned from overseas on Aug. 13, a Saturday night, and found the house now occupied by a cast of Lisa's relatives. He barely had time to gauge their suspicions before a telephone call from Detective Forsythe summoned him to the Rockville Investigative Section.

There, he told the story of Lisa's departure from Dulles and insisted that the investigation of her disappearance ought to be focused in California, not Maryland.

As for the gun, he bought it months earlier, simply because he wanted one. But a few weeks before Lisa's disappearance, he heard about columnist Carl Rowan getting in trouble for shooting a trespasser in his yard. So he disabled the gun and tossed it in the trash.

As for the accidental-death policy, which took effect the month Lisa vanished, he believed "the spouse and children" were the listed beneficiaries. The policy had been purchased through American Express. He couldn't recall whose idea it had been, his or Lisa's.

As for the $44,000, he knew that bank surveillance photos showed him withdrawing the money, but Lisa had given him permission to take it. Her signature was right there on the withdrawal slip. "It was money that was used to pay off some debts I owe," he said, without elaborating. Kai and others already had described him to police as a man who enjoyed betting hundreds of dollars, sometimes more, in Atlantic City casinos and at the mah-jongg table. But Tu denied owing gambling debts.

Before Tu went home, Forsythe asked if he'd be willing to return Tuesday morning for a polygraph test.

"All right," said Tu, but added: "I think you should concentrate on the other first." By this he meant California.

"That's exactly what we're going to do," said Forsythe.

"Don't wait," Tu urged.

Forsythe promised he wouldn't.

"Because I'm not going anywhere," Tu said. "I'm here."

A day before the scheduled test, he packed some clean shirts into his briefcase, bought a plane ticket and left the state.

A few more days passed. And Kai found something else in the house, a Chinese-language Playboy magazine in Gregory's nightstand. It eventually became State's Exhibit No. 32. Kai testified that a boldface excerpt from a piece of first-person mystery fiction grabbed his eye.

Translated, it read:

"I wrapped a sofa cushion around the gun to muffle its report. I fired one round into her chest, another into her open mouth."

The Prosecution's Case Gregory Tu was arrested in Nevada on Sept. 10, 1988, nearly a month after he left Maryland without telling anyone.

In the days while he was gone, the police theory of what happened to Lisa Tu began to take shape. According to trial testimony and court documents, this is what detectives discovered:

At Dulles on July 14, 1988, United Airlines issued a ticket to an "L.L. Tu" -- as in Lisa Lau Tu -- for its Flight 55 to Los Angeles with a connection to San Francisco. L.L. Tu was given seat 38-A. The ticket was used, according to United records. It ended up in a secured box with others collected from passengers as they walked aboard, and had a gate attendant's green slash mark across it.

Police alleged that Gregory either marked the ticket himself and found a way to slip it in the box, or boarded the flight and managed to quickly get off unnoticed.

Among those on the flight was a woman from New Zealand. While she was in Washington, her stepfather, Sir Antony Acland, then Britain's ambassador to the United States, had given her a camera. She took pictures on the plane. Some of them showed seat 38-A. Lisa Tu wasn't in it.

The Los Angeles-to-San Francisco half of the ticket wasn't used -- which meant that L.L. Tu's bag, if one had been checked, should have wound up unclaimed in San Francisco. No such suitcase could be found.

One of the country's foremost document examiners studied the $44,000 withdrawal slip, along with samples of Lisa's and Gregory's handwriting. The expert said the signature was a careful replication -- but it wasn't Lisa's.

On Sept. 7, with Gregory nowhere to be found, a team of detectives and forensic scientists showed up at his empty home with lights, magnifying glasses and an array of chemicals. They stayed for hours.

In the basement, they found no signs of mice. But they did find about 15 reddish-brown stains in various places, none bigger than a dime and some no larger than the head of a pin. Most turned out to be blood. After later genetic tests, scientists said they were virtually certain at least a few had come from Lisa or from a close relative of hers.

At nightfall, they sprayed the basement carpet and stairs with Luminol, a chemical that reacts with iron to give off a green glow, indicating traces of blood that aren't visible to the eye.

The effect was "absolutely chilling," a prosecutor said in court. The search team stood in the dark, transfixed by an eerie swath of pulsating green light. It seemed brightest around where the couch used to be; it went from there into the bathroom, and from the bathroom to the stairs.

Upstairs in the garage was an old Lincoln Town Car that belonged to Gregory. It usually gathered dust for months while he drove his Camaro, family members said. But detectives found the Lincoln clean, with an unrusted scratch running half the length of one side. In its trunk was a meat cleaver, a length of twine, and a sheet of clear plastic about eight feet long and four feet wide. They saw no evidence of blood.

About 7 that night, the telephone rang in the house, and Detective Michael Turner answered it. The caller, a rental-car clerk at the Stardust Hotel in Las Vegas, asked for Gregory Tu. The clerk said Tu had taken out a car the week before and hadn't brought it back.

That was how police discovered where he was -- by "dumb luck," as prosecutor John McCarthy said in court. Las Vegas homicide detectives, alerted by Turner, were waiting outside the Stardust three days later when Tu finally showed up. Montgomery detectives eventually learned that Tu had stayed in a succession of Las Vegas hotels, using a variety of names and playing low-stakes poker for hours at a stretch.

In one of them, the El Rancho Hotel, where Tu was registered on the day of his arrest, police seized several items of evidence that an appeals court later said were outside the scope of their search warrant. Tu is being represented by the Montgomery public defender's office.

Tu told police that a friend, a powerful, private man whose name he must never reveal, had counseled him to leave Maryland and stay low in Las Vegas. This friend, with his California connections, would find Lisa.

Yet in all the months afterward -- through the interrogations, the conviction, the reversal -- neither Lisa Tu, nor any trace of her body, turned up. The detectives kept searching. Turner drove to Massanutten in Virginia's Shenandoah Valley, to a vacant lot Gregory owns, and walked every inch of it, hoping to find a grave. One of the detectives dug holes three and four feet deep in Gregory's prized melon patch behind the Potomac house.

Today, in the Montgomery County courthouse, another jury gathers for Gregory Tu, to weigh his plea of not guilty against a story told by circumstantial evidence. Linda Chung will listen and wait again in despair, still wondering how the story ends.

"In our Chinese tradition," she wrote to the judge in Gregory's first trial, "the deceased must have a place where people can worship and remember her. Although we have gone to a temple and placed her picture there, it just isn't the same. I feel that without her body properly buried, I cannot wholeheartedly relinquish the guilt that I feel. The guilt of not trying my best to locate her. The guilt of not knowing."