On an early spring day in 2018, the faint smell of formaldehyde floating in the air, 26-year-old medical student Warren Nielsen and four of his classmates prepped a cadaver in the chilly dissection lab at Oregon Health and Science University in Portland. Similar groups of five gathered around bodies on the other 15 tables in the anatomy class, all eager to explore the mysteries of the human body they had seen only in textbooks. The cadaver assigned to Nielsen's team was a 99-year-old woman who had died of natural causes. Her name was Rose Marie Bentley, but the students didn't...