Seth Thompson, a $45-$year$-$old firefighter, his wife, Kate, a $42-$year$-$old school teacher, and daughter, Ann, a $17-$year$-$old high school junior, were a stable, middle$-$class family living in a quiet neighborhood in a large city. On her way to work one morning on the commuter train, Kate Thompson experienced a severe stroke and was taken by ambulance to a hospital emergency room. Kate died there. As far as Seth knew, Kate had been in good health and had no medical history to indicate that she might have had a health problem.