I was working for New York City’s Office of the Chief Medical Examiner when the unthinkable happened on Sept. 11, 2001. As a death investigator, I would usually go to an apartment or the streets to investigate a homicide, a suicide or an accidental death. Now it was my job to “work the pile” — that is, to recover and catalog the shattered human remains found in the burning, smoking rubble of the World Trade Center. I had been at the OCME for nine years and had seen all manner of death. After some months my boss, Chief Medical Examiner...