This introductory chapter provides an overview of the book’s main themes. This book is about the situation faced by Supreme Court justices in the McCarthy era, obliged in scores of cases over more than a decade to decide the lawfulness of executive and legislative action directed at alleged Communists and “subversives.” The events demonstrate the Court’s vulnerability in a time of political repression, when a refusal to acquiesce in the repressive actions demanded by popular opinion may lead to harsh attacks in the press and in the Congress, and may result in legislation to curb the Court and limit its independence. The attacks and political pressures deepened existing divisions and rivalries among the justices. The Court’s retreat was accomplished almost entirely in 5–4 decisions. The book’s primary focus is the decisions themselves, which provide the best evidence of the justices’ constitutional views and their responses to the severe pressures under which they labored.