"This book explores three moments of fear in American history, moments when the genial mask of tolerance was cast aside ... The first deals with intolerance during the 1850's, when members of the secret Know Nothing society charged that foreigners were corrupting America. Their attacks were directed especially against Irish Catholic immigrants ... Unit Two considers the Red Scare of 1919-1920 and Unit Three deals with the period after World War II, when the term 'McCarthyism' was coined to define an intense search for disloyal citizens and government officials. In presenting each of the three units, this book analyzes the social setting of intolerance--that is, the conditions that led to the fear that America was in danger of subversion from within."--Author's introduction.