The air conditioner is often hailed as one of the modern world's greatest inventions—yet nearly as often blamed for global disaster. It has changed everything from architecture to people's food habits; saved countless lives, and caused countless deaths. First appearing in 1902, when Willis Carrier, an engineer barely out of college, developed the "Apparatus for Treating Air," everyone assumed it would instantly change the world. But the story of air conditioning and its rise to ubiquity is far from simple.

Where do human societies come from? The drive to answer this question took on a new urgency in the nineteenth century, when a generation of archaeologists began to look beyond the bible for the origins of different cultures and civilizations. Zelia Nuttall threw herself into the study of Aztec customs and cosmology, eager to use the tools of the emerging science of anthropology to prove that modern Mexico was built over the ruins of ancient civilizations.

In 1972, Martha "Marty" Goddard volunteered at a crisis hotline, counseling girls who had been molested by their fathers, their teachers, their uncles. Soon, Marty was on a mission to answer a question: Why were so many sexual predators getting away with these crimes? By the end of the decade, she had launched a campaign pushing hospitals and police departments to collect evidence of sexual assault and treat survivors with dignity. She designed a new kind of forensics tool—the rape kit—and new practices around evidence collection that spread across the country.

On a warm summer evening in 1991, seventeen-year-old Julia Parker was murdered in the Brooklyn neighborhood of East New York. An area known for an exorbitant level of violence and crime, East New York had come to be known as the Killing Fields. In the six months after Julia Parker’s death, 62 more people were murdered in the same area. In the early 1990s, murder rates in the neighborhood climbed to the highest in NYPD history. East New York was dying. But how did this once thriving, diverse, family neighborhood fall into such ruin?

Sonia Orchard was in her forties when she told a therapist about the boyfriend she had when she was fifteen. Sure, he had been a decade older than her, but it was consensual ... wasn't it? To her surprise, Sonia broke down in tears, then began to shake uncontrollably–an unmistakable expression of trauma that lasted for days. She was clearly not okay, but could the relationship she'd thought was love really have been abuse? Had she been groomed?