This book is about the power of communication to do great harm and how civic leaders and engaged citizens can hold other leaders accountable to prevent it. Author Helio Fred Garcia focuses on the language President Trump uses that conditions an audience to accept, condone, and commit violence against a targeted group, rival, or critic. Including a history of such rhetoric, this book identifies a playbook consisting of 12 forms of communication that typically precede genocides and other acts of mass violence. The Rwandan Hutu used 10, the Nazis used all 12, and Trump uses all 12, too. Such language triggers lone wolves to commit violence. Since 9/11, the use of rhetoric that provokes violence has been known as "stochastic terrorism", a phrase that can be confusing and make discussion difficult. Garcia suggests a more accessible name: lone-wolf whistle violence, on the model of "dog whistle" politics. He draws on the most recent scholarship on lone wolves, their mindset, and what it takes to activate them to commit violence, demonstrating how Trump's increasingly dangerous rhetoric throughout his campaign and first term has motivated such individuals. He also describes the changes in the nation's political culture and media that led to Trump's nomination and presidency but also profiles leaders who dialed back their rhetoric when it was shown to put people's lives in danger. Words on Fire closes with a call to action: we all - civic leaders, engaged citizens, journalists, and public officials - must recognize this phenomenon so that we can take steps to hold our leaders accountable in the future.