Wendy shifted restlessly in her seat. "Chris, can we please change the subject? None of what you're asking can happen."

"Honey, just pretend for the sake of argument: If you had the option to add another, say, fifty years onto your lifespan without aging, with me and your sister…"

"And how would you explain it to your neighbors when they grew old and you didn't?"

"We'd just move someplace else."

She started to laugh. "You mean every ten or fifteen years while everybody else is turning gray, we just pack up and go to another city?"

"Something like that."

"We'd be living like fugitives."

"Say we moved to your family place in the Adirondacks?"

"You mean live the last eighty years of our lives hiding in the woods? Frankly, I think I'd rather die young."

They were on their way to Logan airport to pick up Wendy's sister Jenny and her new baby who were visiting for the weekend. While they were in for Wendy's birthday, Chris was privately celebrating the birthday of a mouse.

Not Mickey. That was two years ago-and, Wendy swore, never again. No, this was a real mouse.

Although mus musuclus sextonis could be mistaken for any other laboratory rodent, it was a rare mutant with the dubious distinction of being the shortest-lived mouse-a mere eleven months compared to twenty-three for most others. Located at a breeder in Maine, Chris had ordered some five hundred of the animals over the years. Of the original batch, over 60 percent had defied their DNA clock by a factor of four. And one, a slender albino agouti male with pink eyes, had outlived them all as the sole survivor of years of secret experimentation-the one Chris had named Methuselah because he had exceeded his life expectancy by a factor of six, and today was celebrating his sixty-sixth month.

The best-laid plans of mice and men had not gone awry: Iwati's flower had worked!

Chris had been as good as his vow. For six years only one other person at Darby Pharms knew of his research. They had worked on the sly-nights and weekends-isolating, purifying, synthesizing, then testing the flower extract. And Chris got away with it because as senior researcher he had complete autonomy in the lab and could mask requisitions for material and animals. No one else from top management down had any inkling that during downtime on the apricot toxogen Chris was at work on the tabukari elixir. To the casual observer Dr. Christopher Bacon was the ideal employee-a man dedicated to his science, his company, and his fellow human beings.

Like the apricot toxogen, synthesis of tabukari was a complex process, but unlike Veratox the yield was very high. The active ingredient contained forty-six molecules, including a slight molecular variation of a steroid, fluoxymesterone, a hormonelike compound which Chris had never seen in a plant before-what he named tabulone.

In addition to testing tabulone on mice, Chris also applied it to cell cultures with astounding effects. From the medical literature he knew that normal, noncancerous animal cells reproduced a finite number of times between birth and death. For mice, it was an average of six replications; for chickens, twenty-five; for elephants, one hundred ten. For humans, about fifty. In a Petri dish four years ago, Chris had made a breakthrough discovery. He had taken two different batches of mouse brain tissue. One he treated with fluid nutrients and a nontoxic blue stain and incubated the mixture at body temperature. He did the same with the other but added tabulone. After five days, the first batch went through its full six replications, then died. Under the microscope, the walls of the cells had deteriorated to let the blue stain seep through. However, the cell batch treated with tabulone remained perfectly clear and healthy as on Day One. For all practical purposes, tabulone had stopped the biological clock. Today those same cells were still alive and thriving.

Somehow, tabulone had produced a protective shield around the test cells. Chris didn't understand what was happening on the molecular level, and he wished he could consult a geneticist. But six years and three hundred mice later he knew he had developed the closest thing to biological perpetuity. What started out as a quest for the perfect human birth control had, ironically, produced an eternal mouse. And Darby Pharms Inc. never knew. Nor would he tell them until he had worked out some nasty limitations of the compound.

Even then Chris was not sure. What staggered his mind was the magnitude of the implication: If tabulone could work the same for humans, he was at the threshold of the most astounding breakthrough in medical science-one that would redefine the very concept of life.

"You mean they don't die?" Wendy asked.

"No, they'll die eventually, but not from diseases associated with age-kidney failure, heart and liver diseases. Theoretically they could go on for a few more lifetimes."

"But a few mice outliving their life span doesn't mean you've discovered the fountain of youth for humans. You're a scientist, Chris. You know better than to make wild speculations."

"What about Iwati?"

"You want me to believe that some New Guinea bush-man who claims to be a hundred and twenty three and doesn't look a day over thirty? Give me a break."

"What if he is?"

"Then I'd pity him because he'd be forced go on long after the people he loved grew old and died. He'd be a freak alone with his secret."

A freak alone with his secret.

The phrase stuck in Chris's mind like a thorn.

Maybe that was why Iwati had returned to the bush. It was the one place where time didn't move, where he could live to a hundred and fifty or more and never feel the press of change. In Port Moresby or Sydney or any other city, the future was happening by the moment. But in the Stone Age Papuan highlands, he had found indefinite life and exalted status. He was the Tifalmin's Constant Healer, dispensing balms for this ailment and that while keeping to himself the ultimate balm-the taboo to which only his offspring would be privy. And the ultimate bequest of a father to his firstborn son.

"Chris, death is what makes us human," Wendy said. "I want to live only long enough to become old."

They emerged from the Callahan tunnel to a line of traffic and turned right, toward the entrance of Logan Airport.

"Wendy, most of the people in these cars won't be here in thirty years. They'd kill to double or triple their stay. You're an English teacher: Imagine what Shakespeare could have created had he lived another fifty years. Or Michelangelo or da Vinci or Einstein. The mind boggles. Just imagine how much more writing you could do, how much more life you could enjoy."

"'Death is the mother of beauty,'" she quoted. Her voice was now flat, the earlier efforts to play along had vanished.

"Maybe, except that Wallace Stevens saw no alternative."

"Chris, we die for a reason. You're tampering with Nature-with processes refined over billions of years. And there's something dangerous in that. Besides, have you considered any of the social problems if the stuff actually worked on people-such as who could afford it? Or the population nightmare? Or if the stuff fell into the hands of criminals or a Hitler? The good thing about death is that it gets the bad guys too."

Chris made a dismissive gesture with his hand. "Precautions could be taken against all that. The point is, I like being alive. I like the moments of my life. And in thirty years I'll be dead forever. You know what forever means? It means never being conscious again. It means never waking up the next morning and seeing the world, of thinking, of being aware of colors and sounds. It means never seeing you again, and that sickens me."