BY the time he was 76, my father was frail. His balance was poor and he had trouble walking. He lived alone in Baltimore in a big house full of stairs, and watching him come tottering down those stairs was terrifying. Each time, I thought he might fall. He refused to make the house safer -- no stair lifts, no grab rails (they would disfigure the house, he said) -- and would not consider living anywhere else. When my brother and his wife invited my father to move in, the invitation was vigorously declined. And we lived in three different cities, far apart.