Ann Humphry's pale blue eyes betray a sense of anguish and fear as she welcomes a visitor to her rustic farmhouse in Monroe, Ore. Since the removal of a cancerous tumor from her breast last September, the 5'7" blond woman has lost more than 20 lbs. and suffered chronic anxiety about her health. Worse, at age 47, facing a life-threatening disease, Ann found herself suddenly abandoned by her husband. Just three weeks after her surgery, and four days after Ann began a grueling regimen of radiation and chemotherapy, Derek Humphry, 59, telephoned home during a business trip to say he was leaving her. "He left a message on the answering machine," she says. "That's how I knew he wasn't coming home."

By walking out on his wife, Derek Humphry also appeared to be acting inconsistently for a man with his chosen role: He is co-founder and leader of a humane "right-to-die" group dedicated to people with terminal illnesses. Ironically, Humphry's first wife, Jean, was also a victim of breast cancer and died in his arms in 1975 after she drank a cup of coffee that she knew he had laced with secobarbital and codeine to end her suffering. Less than a year later, Humphry married Ann, with whom he co-authored Jean's Way, an account of his first wife's suicide. In 1980 Derek and Ann co-founded the Hemlock Society to crusade for voluntary euthanasia and for legislation that would allow doctors, without fear of prosecution, to assist patients who wish to commit suicide. In the next decade they built a powerful national organization with 30,000 members and gross revenues of nearly $1 million a year, mainly from dues and book sales.

Both Derek and Ann now seem bent on destroying each other's reputation. Derek has barred his wife from Hemlock's headquarters, changed the locks on the offices and forbidden employees to associate with her; the board also removed Ann from the post of treasurer and placed her on medical leave, initially for just three months. Ann in turn has waged a campaign to have him ousted as executive director, through lobbying letters to the board and in occasional statements to the press. The war escalated markedly when, says Ann, Derek on Feb. 15 left another message on her answering machine threatening to reveal details about the 1986 double suicide of her aged parents, Ruth and Arthur Kooman, in Boston. "If you continue this stupid fighting one more step, I shall give your sister and nieces a full statement that you committed a crime in helping your parents die," said Derek. "They will then be able to sue you for the $300,000 you inherited."

Meanwhile the membership of the Hemlock Society has been busy choosing sides in the marital dispute. Jean Gillette, a 72-year-old executive-board member who survived a radical mastectomy herself 20 years ago, portrays Ann as hysterical and blames her for talking publicly about the entire brouhaha. "This is really, in my way of thinking, a very disturbed woman," says Gillette. "If she had handled this thing differently, she might have had great sympathy on the part of many of us." By contrast, former board member Henry Brod, 63, who resigned in a disagreement with Derek, says, "Derek has behaved viciously toward his wife. I thought Hemlock was all about compassion and decency toward people desperately ill." For his part, Derek expresses no regrets about leaving Ann. Sitting at his desk in the Hemlock Society's Eugene, Ore., office, he speaks with almost clinical detachment about his breakup with Ann. "I reviewed the facts and decided I couldn't live with her anymore," he says. "She handled her cancer so badly, I'm sorry to say. She became so neurotic about it that I was falling to pieces. I couldn't take it."

The child of a broken marriage, Derek was separated from his mother as an infant in Bath, England, and began shuttling between foster homes at age 7, when his father was imprisoned for a year for embezzlement. Setting out on his own at age 15, he gradually worked his way up from Fleet Street messenger boy to become a reporter for the London Times. He raised three children with Jean, his wife for 22 years.

Ann Wickett, a native of Boston, had attempted suicide and been hospitalized for several months in 1969, after the failure of her two-year marriage to a Toronto lawyer. She was a Ph.D. student in literature at England's University of Birmingham in 1975, when Derek was one of 100 men who responded to her personal ad in the New Statesman, a political weekly. "On our first date Derek told me about Jean and how she died," Ann recalls. "I was very moved by it all." They were married in 1976.

It was Ann's suggestion that the couple collaborate on Jean's Way, published shortly before they moved to Los Angeles in 1978. Two years later the Humphrys launched the Hemlock Society. In addition to lobbying for "right-to-die" statutes nationwide, the group has published Let Me Die Before I Wake, a guidebook which includes specific doses of drugs to induce "peaceful self deliverance" and Double Exit, Ann's fictionalized account of her parents' death 3½ years ago.

Derek claims his marital problems with Ann stem in part from "her bitter and continued condemnation of what she calls my failure to support her over her parents' double suicide." He also speaks of her rapid mood swings and unrelenting antagonism toward his children. Nonetheless, after the inheritance from her parents helped finance the Humphrys' move to a 50-acre farm north of Eugene in 1988, Ann thought their marriage was on the upswing.

Soon after Ann returned home following surgery last September, she found Derek in the kitchen, sobbing. "He said, 'This reminds me so much of Jean and when she was dying.' I felt so sorry for him." But Ann quickly grew to resent Derek's apparent lack of sympathy for her. In a statement that he circulated and titled "Why My Marriage to Ann Wickett Failed," Derek wrote that "she kept insisting she was terminally ill even after the oncologists assured both of us that she was not so and that a return was highly unlikely...she literally demanded that I cry for her in the same way as the book Jean's Way reports that I did for my first wife."

The night before he left Ann for good, Derek apologized for not being attentive to her needs. "We became very loving," Ann says. "He made love to me that night and he made love to me in the morning. It was very moving." She believes now this show of affection was part of a plan. "He was saying goodbye to me," she says.

In December Ann suffered a mental collapse and spent eight days in the psychiatric unit of a local hospital. In the meantime Derek tried to limit Ann's medical leave to three months and force a gag order on her as a condition of remaining on Hemlock's payroll. She refused, and in January the board of directors avoided a confrontation by voting to continue her $1,250 monthly pay and benefits for six months. At that meeting, Julie Horvath, a friend of Ann's, was shocked by the virulence of Derek's anger. "You could see the hatred in his eyes," says Julie. "It's like he's trying to erase Ann out of existence."

Pending the resolution of her campaign against Derek, Ann has resigned herself to being locked out of any real decisions at the society she helped found. "I'm an embarrassment to Hemlock because I got cancer and my husband left me," she says. "They wanted me to just keep my mouth shut." Derek is unrelenting. "I don't owe Ann anything," he says. "There's no requirement to this job that I be a saint. There's no requirement that I martyr myself to a desperately unhappy marriage."

—David Grogan, Jeanne Gordon in Eugene