Suicide by stabbing is rare–1 or 2 percent of the annual U.S. total. But ““executive suicide’’ seems to be growing more common in the 1990s. ““Nobody’s guarding the guardian,’’ says Ron Maris, head of the Center for the Study of Suicide at the University of South Carolina. Maris coined the term ES for the still largely uncharted phenomenon in the 1970s. But interest in it has been rising in the wake of two prominent victims from the Clinton administration: White House lawyer Vincent Foster and Adm. Michael Boorda. What defines ES, beyond the fact that even people at or near the top of a hierarchy can kill themselves? There are several markers (chart), but the main one is surprise. Two thirds of all suicides signal their intent in advance, in words or deeds. Executive suicides–Foster, Boorda, Curtis et al.–almost never do. ““Most men have a hard time asking for help,’’ says Washington University psychiatrist George E. Murphy. ““But if you’re an executive, one thing you never let anyone see is your weakness.''

Despite John Donne’s famous line, some men do end up as islands–and that seems to have been the case with John Curtis. Born in Abilene, Curtis graduated with honors from Texas Tech University in 1969 and promptly married his grade-school sweetheart, Kathi. ““I sat next to John in the sixth grade and loved him from that moment,’’ she said after he died. Together, they raised three children–two high-school valedictorians who became CPAs, just like Dad, and a 15-year-old still at home. Together, they joined the evangelical church where Curtis served as a trustee, always willing to come by with a yellow pad and help a parishioner struggling to climb out of debt. Curtis rose swiftly through the ranks at Luby’s–chief financial officer in 1988, a Harvard Business School fellowship in 1994, president in 1996, CEO last January. No one in the family seemed to sense anything wrong the night he left for Motel 6 instead of the airport. ““I have no doubt,’’ Kathi told a memorial service last week, ““that some oppressive darkness overtook his mind.''

Ralph (Pete) Erben, Curtis’s mentor at Luby’s, saw at least a hint of twilight. Yes, he admits, Curtis did seem anxious about the board meeting in Phoenix. Erben, who resigned as Luby’s chairman last week, told NEWSWEEK about their last meeting. Among the worries two days before the suicide: a profit margin of 6 percent for the quarter, down from the usual 9 percent. ““I said, “Hell, you’ve been CEO for two months. Blame everything on me!’ ''

And there was more. The week before, Erben had broached to Curtis an idea that, in historic terms for Luby’s, was almost unthinkable–closing its nonperforming stores at the rate of 1 percent a year while continuing to grow in more promising locations. Luby’s, which operates 226 units in 11 states from Florida to Arizona, is the industry leader in the cafeteria business. Nationally that’s a shrinking sea, but Luby’s has remained a buoyant ship, posting 26 straight years of increasing sales and earnings per share. It has closed only two stores in its 50-year history.

In an era of corporate bosses who lay off thousands without so much as an attack of indigestion, what makes a CEO kill himself? The answers are usually speculative and probably as diverse as the ES victims themselves. One possibility in Curtis’s case: he could not bear the shame, or perhaps the cruelty, of laying off 1 percent of Luby’s 13,000-person work force. His wife, Kathi, reportedly told police her husband had been having trouble sleeping for about two weeks, and that ““store closings out of state’’ were one reason. Another: at the annual shareholders meeting in January, the new CEO said one of his goals was to bring Luby’s profit margin–already twice the industry average–eventually into double digits. In Phoenix, he’d have to tell the company’s 10 directors the numbers were headed down, not up.

Curtis kept the depths of his despair a secret from his wife, his mentor, his pastor and everyone else. He was, by all accounts, a courtly but taciturn man who did not abuse alcohol, own a gun, see a shrink or lose his temper. One Luby’s research-department employee saw the CEO’s hands tremble the Monday before he killed himself–but that was all. The next day at 5 p.m., leaving early for Phoenix, Pete Erben poked his head into Curtis’s paneled office on the fourth floor. ““See you Thursday,’’ Erben said. ““OK, see you then,’’ Curtis answered chipperly. Erben desperately wishes his protEgE had sunk his head into his hands instead. ““I could have shook his tree and said, “Hell, nothing’s that important.’ But I didn’t have a clue.''

Curtis left none behind when departing his office Wednesday evening. Two newly published cookbooks, which the CEO planned to send to store managers to keep the buffet line current, sat on the shelf behind his mahogany desk, neat as usual. On Wednesday night, he prayed with his wife as was their custom. An hour later, at about 10:30, he drove to the Motel 6 eight miles down the road, past a Luby’s, and checked into a room at the back with a view of the Dumpster. Sometime during the night, he slipped home again and left a note saying he planned to kill himself in room 214. Kathi found it the next morning.

Despite the tumult at the top, the value of Luby’s shares on the New York Stock Exchange ended the week as solid as steam-table meat loaf. Curtis’s friends and colleagues were more disturbed. ““We’d like to understand this,’’ says Robson, the executive vice president. ““I don’t know that we ever will.’’ Bill Biggadike, head of the men’s group at Curtis’s church, can’t fathom the method his friend used. ““My feeling,’’ Biggadike offers, ““is that just like the heart wears out, sometimes the brain does, too.''

Next month, the annual conference of the American Association of Suicidology will devote a two-hour session to the deaths of Foster, Boorda and Curtis. Experts will hear the originator of the term ES argue for better monitoring systems for the uniquely isolated subset at the top of the executive heap. ““Nobody’s looking now,’’ says Ron Maris, ““and if you don’t look, you don’t find.’’ It’s not just lonely at the top. Sometimes the loneliness can prove deadly.

Warnings signs: Depression, a sense of hopelessness–the warning signs for men in charge are the same as for most people, but they are often covered up by the victim. Symptoms may go untreated because no one has the clout to force execs to get the help they need.

Psychological profile: Top executives in trouble perceive their problems in a distorted way. They’re liable to feel intense shame for failures. Men who are used to being in charge may see suicide as an aggressive solution.

Methods: Most suicides involve guns. Other methods are carbon monoxide poisoning and private-plane crashes. Some suicides may lokk like accidents, for insurance or face-saving reasons.