An accident brings sudden change to life, but Alzheimer's disease is a slow process that twists and disfigures thinking processes and personality and forever changes a person's relationships. The realization that dementia is manifesting itself comes to family and friends in gradual stages, and the coping strategies are painfully wrought.         My father, Neil J. Niemi, had experienced an extraordinary life before Alzheimer's disease took hold of his mind his last eight years. His life encompassed more change than will likely be duplicated on this planet as he moved from handling a horse-drawn plow to helping plot the trajectory patterns for man landing on the moon.         His Finnish parents were drawn to North America by promise of free land on the Saskatchewan prairies. He and a twin brother were born in January, 1913, during a blizzard. One of the babies was fat and content; the other was skinny and screaming. The family feared one wouldn't survive, and they were right: the fat baby died and the skinny one lived and was named Niello Johann or Neil John.         Neil's upbringing followed the immigrant tradition of minimal schooling and much work on the farm to ensure family survival. Neil displayed extraordinary ability, especially in mathematics. The teacher in the one-room schoolhouse would write a long list of numbers on the chalkboard for an addition exercise; Neil would walk up to the board and write the answer without calculation.         Formal schooling ended in grade eight, as was customary on the prairies in the 1920s, and Neil spent years working the family farm with his ten brothers and sisters, and tinkering in the family's blacksmith shop. A younger sister who had resolutely pressed on with her education and become a teacher nagged her shy, bookish older brother to complete high school by correspondence course. He studied in the hayloft and favored science, technology, and mathematics. One book on electronics had symbols which he at first skipped, but then realized had to be learned. He ordered a book on trigonometry and taught himself the subject in two weeks.         His grades were so good that he won a scholarship to the University of Saskatchewan in 1939 to study physics. He was twenty-six and continued to excel in his field, married a school teacher from his district, undertook graduate study, and immigrated to the States with his wife and daughter in the late 1940s. When Sputnik changed world history in 1957, Neil was transferred by the Chrysler Corporation from automotive to space research, specialized in guidance systems, and worked with Werner von Braun's team of rocket scientists spirited out of Hitler's Nazi Germany.         After a successful career, parenting three daughters, retirement, and caring for a wife with Parkinson's disease until her death, Neil, in his mid-seventies, began to display signs of what my two sisters and I determined to be dementia. I discovered wizened, blackened vegetables on a shelf in the utility room identified only by the shriveled bag around their mummified remains announcing "carrots" and wedged between old magazines and tools. Neil claimed ubiquitous, crafty thieves and mischief makers broke into his house and stole keys, hid favorite sweaters, and diluted the hand lotion. He displayed a franticness, a frenzy when he couldn't remember routines. My sisters and I struggled to respond rationally to his irrational behavior and fears.