On December 14, 2012, 26 people at Sandy Hook Elementary School in Newtown, Conn., including 20 children barely older than toddlers, were shot and killed. It felt like a line in the sand, on gun violence and safety. Instead, nine years on, Sandy Hook has become a foundational story, and a symbol: of how malevolent, profit-motivated actors use the internet to terrorize the vulnerable, even the families of murdered children, and how conspiracy has gained traction in our world. In the wake of the tragedy, parents of the young victims have been accosted on the street. They are harassed online. They are stalked and forced out of the towns they live in. Someone shot a rifle into the home of one parent. At the center of conspiracy theorists' crusade is Alex Jones's InfoWars, where hoaxers air noxious theories and raise money. Through exhaustive reporting, narrative storytelling, and intimate portraits, Sandy Hook is the definitive book on one of the most shocking cultural ruptures of the internet age.