For 60 years, since she was 24, she had been constantly at his side, and that is where she was when the accident happened. He was coming back into the living room from the balcony, where he had been sitting in the afternoon sun, and he lost his balance.

That happens often, despite four-pronged canes or walkers, when you are 90 years old with a long history of Parkinson's disease and the aftereffects of a stroke which weakened the right leg.

She tried to grab him as he fell sideways, but she weighs only 90 pounds, so his weight carried both of them to the floor. He gashed his cheek when he hit, but not seriously. But her legs got tangled with his and he came down on top of her, breaking her right hip.

They then experienced the nightmare which all elderly people, living alone or in couples dread: being injured and without help. They lay there on the living-room rug, 15 feet from the nearest phone.

Nina recalls saying to my father, "We're not going to get out of here unless we can holler for help." The sliding door to the balcony was still open, and when they started to shout, people in the neighboring building heard them. Rescuers broke open the front door of the apartment, summoned an ambulance and by the time I was called, across the country, they had been through the emergency room and were lying in adjoining beds in a Santa Monica hospital.

The next morning, they looked tiny and fragile and, in more than a physical sense, broken. But the two weeks since then have taught me a lesson in human resilience which I hope I will not forget. I write, not just in tribute to them, but to reinforce in my own mind -- and in yours, if you need it -- the irrepressible character of individual spirit.

I suppose I should not have been surprised. They are fiercely independent people, Nina especially. She has a will of steel. She was a "liberated woman" of the 1920s, but the more recent women's movement came too late for her to fulfill her full talents.

If she came out of college today, her ability and determination would make her a successful executive. As it was, she ended her formal education with high school, married early and focused her formidable energy on her one husband, her one son, her volunteer community work and her unquenchable thirst for reading, learning and arguing.

She has never been accused of being an easy person. She is blessed -- or cursed -- with a belief in human perfectibility, and she has fought with everyone of any importance to her who fell short of that standard, as everyone did. But she was usually toughest on herself.

When my father retired afer 50 years of small- town Midwest dentistry, they scorned the idea of moving in with (or even close to) their son. At 67 and 73, they left their home and their home town, came west, found an apartment in a neighborhood where they could walk every day, formed a new circle of close friends and built a new life on their own.

Long after it became more than she could really handle, long after her own health and well- being could tolerate it, my mother insisted she would keep house for my father. She ragged him constantly to overcome or ignore his own physical handicaps.

This was not without its costs to both of them, and it is certainly not a model everyone would wish to follow, or should attempt. There is a process of gradual isolation which almost all very old people experience, as the friends and family members of their own generation die.

When this is exaggerated by an effort to function as an autonomous household, independence can easily become isolation.

But that does not make it any easier to give up that independence. The real threat of this accident, far greater than the physical injury, was the risk of dependence. The hip can be pinned, but there is no surgery for a broken lifetime pattern.

They are fortunate to have found an excellent residential-rehabilitation center, where they can live together while Nina receives the physical therapy she needs to regain mobility. The change of location and circumstances has tested both of them, and they are responding with a resiliency that would do credit to people 50 years younger.

The long-term housing and living decision is a question they have wisely decided to postpone for a time. When Nina has regained some of her strength and mobility, they will decide. Independently, of course.

They are not in this alone. America has seen a rapid increase in the numbers of very old people and a simultaneous breakdown in the extended- family pattern of living. The Census Bureau says that among the 27 million people over 65, more than eight out of 10 live either by themselves or with a spouse. Only one in eight lives with other relatives; only one in 20 in some kind of communal-care facility.

All of us who live long enough will, I suppose, face the choice of how to fashion those final years for ourselves. I hope I have the courage and wisdom to do it as well as the woman and man of whom I write.