Among the most far-reaching outcomes of the Mongol moment in world history was the spread all across Asia, the Middle East, Europe, and North Africa of that deadly disease known as the plague or the Black Death. While the Mongols certainly did not cause the plague, their empire facilitated the movement not only of goods and people but also of the microorganisms responsible for this pestilence. Its sudden arrival in the late 1340s, the enormity of its death toll, the social trauma it generated, the absence of any remembered frame of reference for an event so devastating — all of this left people everywhere bewildered, imagining the end of the world. The sources that follow illustrate how people in various cultural settings experienced this initial phase of the catastrophe, sought to understand what was happening, and tried to cope with it. This exercise begins with three general accounts of the arrival of the plague — in the Islamic Middle East, Western Europe, and the Byzantine Empire — followed by five sources that focus on more specific aspects of this hemispheric pandemic.