This article is an historical ethnography of the popular conceptualizations of crowd behavior during the pogroms against the Armenians in the Ottoman East in 1895–1896. It draws on contemporary sources like official telegrams, governmental reports, letters of American missionaries, and Armenian periodicals to show that observers with otherwise highly conflicting views described the structure of the event in the exact same way: as an outcome of sinister deception. Without exception, all parties told some story of deception to explain the violent attacks of the Kurdish semi-nomadic crowds on the Armenian neighborhoods of the city of Harput. The article analyzes these cases of disguise, deluding, and inculcation to reveal how contemporary observers theorized crowd behavior in general and the atrocities they witnessed in particular. They did not perceive violence as an index of social distance or deep societal divisions. On the contrary, they described a world in which Armenians and Muslims lived a shared life, and where one attacked the other only when deceived. Methodologically, the article lifts barriers between intellectual history and social history on behalf of an historical ethnography of people's theories about their own society.