The Florentine Dominican Riccoldo da Monte Croce was a thirteenth-century missionary and apologist to Eastern Christianity and Islam, who travelled throughout the Middle East during a period in which the Latin Church was in ferment, challenged by the internal danger of heresy, and external threats from Mongols and Muslims. Yet, this essay places Riccoldo, whose life has been the subject of little extended study, particularly in English, at the end of a thirtyyear period of optimism and anti-crusade feroour in the West. Not only was Europe rediscovering Eastern Christianity, but there was hope of the possible conversion of both Mongols and Arabs to the Latin rite, or at least political alliances with the Mongols against the Muslim empires. The first part of Riccoldo’s journey was a pilgrimage to the Holy Land, where his faith and sense of mission were renewed. During the second, and longer part of his journey, Riccoldo encountered many people of different races—Turks, Kurds, Arabs and Mongols—and religions—Christians of all persuasions, Buddhists, and both Shiʿi and Sunni Muslims. While his initial impression of Muslim spirituality and ritual was positive, it is radically changed when, while in Baghdad, he witnessed the display of prisoners and booty resultins from the fall of Acre in 1291. Riccoldo’s subsequent crisis of faith called into question his belief in the providence of God, and would radically colour his understanding of the place of Islam in what he had heretofore perceived as ‘Christian history’. For Riccoldo, the fall of Acre would have to be answered from a Christian theological perspective, with lasting significance for the history of Muslim-Christian relations.