You think you know which side you're on when it comes to physician-assisted suicide and euthanasia? When you get to that place where your loved one wants to die--and wants help from a physician in doing it--you won't be on safe or easy moral ground.

If you want to find out how complicated dying can be, go to a play called "A Question of Mercy," running through July 4 at the Olney Theater.

Its message is summed up by the "am" words: ambiguity, ambivalence. And for those who know the territory of troubled dying, amen.

The play by David Rabe, based on a story by physician-author Richard Selzer, is about Selzer's own experience when he was asked to "intervene" and relieve the suffering of a man in the debilitating, humiliating end stages of AIDS. The patient needed a doctor to instruct him on taking a massive dose of pills, and if that didn't kill him, he wanted the doctor to administer a lethal injection of a narcotic. In other words, he wanted the doctor to kill him.

It's a true story. Selzer had retired from surgical practice when he was approached by an acquaintance, a man who was taking care of his dying lover. "I didn't want to do it," he recalls, but he was drawn into the life of this couple, touched by their affection for each other and moved by the man's suffering. Selzer kept going to their apartment until "in the end I was persuaded I was going to do it."

The play reenacts the real-life drama. "It's a moral dilemma," continues Selzer. "My thinking went: I have to relieve this man's suffering somehow. I'd smother him if I had to. But I was fearful of being found out. I'm not a killer. There's a line you have to cross when you end a life."

In three decades of medical practice there were times when Selzer put an end to suffering and let death happen, either by prescribing medication for pain or by withdrawing support systems. But this was different. The patient was very much alive, and he wanted Selzer to take an active role in bringing on death.

"My resolve not to get involved--my resolve to protect myself--was worn down," Selzer recalls. As they plotted how to do "it," he became less a physician and more the third person in an intense triangular relationship. His emotions were swayed to the point where he felt, "I must relieve this man and that's it," explains Selzer. "I was going to do it and take the consequences. I never confided in my family or anybody. It was very lonely. I was simply going to kill him."

Here they were--three ordinary people bound together, "plunked down in front of the toughest dilemma," says Selzer. "How are we going to handle it? We did the best we could. I stayed with them out of a feeling that I couldn't abandon them."

And then in the end, he didn't do it.

A twist in the plot--in real life and in the play. Another person comes on the scene--a woman who is a friend of the caretaking lover. She is rational and has emotional distance. She takes Selzer and her friend aside and tells them they are crazy--giving a lethal injection is illegal. They will all go to jail. She prevails and Selzer is essentially fired from the job.

They don't communicate all this to the patient, who takes the massive dose of pills, as planned.

"I did not tell him I would not be there. It was cowardice," says Selzer. "I felt I had betrayed him. I felt awful."

Another twist in the plot: The patient doesn't die after the overdose. When he is found the next day, he is rushed to the hospital and given the high-tech works to keep him alive. Selzer visits the patient, who is semi-comatose and can only nod and gurgle and shake his head. Selzer asks: Do you want to live? The patient nods affirmatively.

This is also part of the human condition. A person who wants to die on Tuesday wants to live on Friday.

After a performance of the play in Atlanta, Selzer was standing in the lobby and a couple of women came up to him and said: "We're so glad you didn't do it." He smiled and then a man came up to him and said: "Why the hell didn't you just do it and get it over with?"

"Ambiguity is the thing," says Selzer. "I don't think anyone can come down on one side or the other. We're frail human beings. We flounder."

The play humanizes all the cold research on issues of assisted suicide and euthanasia. A report last year on cancer doctors in the Journal of the American Medical Association found the same high level of angst and ambivalence that plagued Selzer and the characters in "A Question of Mercy."

"They had great difficulty doing it," says the report's author, Ezekiel J. Emanuel, head of clinical bioethics at the National Institutes of Health (NIH). "The Kevorkian notion that this is a walk in the park is ludicrous. Families tend to have a lot more angst than the way it's portrayed in the media." NIH found the play so provocative that it held a panel discussion after the performance.

There's no avoiding the issue of dying, yet the demand for physician-assisted suicide is actually quite rare--and in most cases involves cancer patients. Still, it is an unfixed point on the public's moral compass that will keep wavering as people live longer and medicine's power to treat sometimes outpaces the body's capacity to heal.

Perhaps that's the way it should be.

"A Question of Mercy" makes clear that there is no easy answer to assisted suicide and euthanasia. It's much more complicated than legalization--or no legalization.