I got stuck on the sadness of this for a few days, and then I decided to try and understand it better. While Hatcher recovered on the couch—doctor’s orders for him were to chill out and not move much or do much—I called the neurology department at the University of Colorado’s Anschutz Medical Campus in Aurora. Dr. Christopher M. Filley, the department’s director of behavioral neurology, helped me grasp what might have happened. “From what you told me, your son did not appear to be sufficiently injured to prompt someone on the slope to stop and see how he was doing,” he said.