When Rosina Hernandez was in college, she once attended a rock concert at which one young man was brutally beaten by another. No one made an attempt to stop the beating. The next day she was struck dumb to learn that the youth had died as a result of the pounding. Yet neither she nor anyone else had raised a hand to help him. She could never forget the incident or her responsibility as an inactive bystander.

Some years later, Rosina saw another catastrophe. A car driving in the rain ah…