William of Baskerville is sent to a monastery in 1327 to mediate between the Pope's delegation and Michael of Cesena and also investigate the mysterious deaths of several monks. During his investigation, William discovers that the deaths were linked to a rare copy of Aristotle's Poetics that was being kept in the monastery's library. Possession of the forbidden book led some monks to kill themselves or others in order to examine or retrieve it, culminating in the accidental burning down of the library and monastery.