The year is 1327. William of Baskerville, a Franciscan friar, and Adso of Melk, a young novice travelling under his protection, arrive at a wealthy Benedictine abbey somewhere in Italy on an important secret mission. A group of Franciscans has come under fire from Pope John XXII, who suspects them of heresy. The Holy Roman Emperor, Louis IV, has aligned himself with the Franciscans, and the abbey has been chosen as a neutral location for a theological disputation, with representatives coming from both sides. Upon the arrival of William and Adso at the abbey, they learn that this peaceful community has been disturbed by the mysterious death of a young illuminator, Adelmo of Otranto. The abbot pleads with William to solve the mystery before the arrival of the two delegations.

As the novel unfolds, several other monks die under mysterious circumstances, and William must play detective. His tools are the logic of Aristotle, the theology of Aquinas, and the empirical insights of Franciscan theologian and English philosopher Roger Bacon, whom he reveres. He collects evidence, deciphers secret symbols and coded manuscripts, and explores the eerie labyrinth which protects the abbey’s library. The prodigious collection of books is at the heart of this mystery, for the library is forbidden to all but three men: the abbot, the librarian, and his assistant.

The novel is divided into seven sections, each corresponding to the seven days that William and Adso stay at the abbey. Each section is divided into periods corresponding to the strict liturgical hours in which Benedictine monks are awake, during which they are required to pray, study, eat, and work. On the first day, the novel introduces the principal characters, the layout of the abbey, and the central conflicts within the Catholic Church, and between the Church and the imperial powers of the secular world. The abbey’s scriptorium, the seat of all learning in the medieval monastic world, is also introduced.

Under the surface of this orderly community are countless secrets and rivalries. In the scriptorium, William and Adso meet the stern librarian, Malachi, keeper of the library’s secrets. They also encounter the elderly, blind Jorge of Burgos, the second oldest monk in the abbey, whose ideas about the dangers of reading cast an immense shadow over the library. At their very first meeting, Jorge and William spar about the dangers of representation, and especially the dangers of laughter. It is the first of several such debates, and this moral conflict is threaded throughout the novel.

On the second day, Venantius of Salvemec, translator and scholar of Greek, is found dead in a vat of pig’s blood. To solve the crime, William and Adso must make their way through the mysterious labyrinth that guards the library. They are unable to penetrate its darkest secrets, and vow to return. They manage to decipher the signs and symbols by which the books are organized, and realize there is a secret room, known only to a few. This secret room is called the finis Africae, but that is all they know. Benno of Uppsala, a monk who is a student of rhetoric, reveals that Malachi and Berengar of Arundel, the assistant librarian, are lovers, but Berengar had been trying to seduce Adelmo, who was young and handsome. On the night of Adelmo’s death, they had a sexual liaison, and Benno claims that both Jorge and Venantius were aware of these indiscretions.

By the third day, Berengar is missing, and the sense of doom intensifies. The abbey’s seedy underbelly is further exposed as we meet several of the itinerant men who have taken refuge in the abbey after a life of wandering and misdeeds. Everybody is a suspect and no one is safe. On the third day, Adso commits a carnal sin, succumbing to the sexual advances of a young peasant girl from the local village. He confesses and is absolved by William, for his master is wise and compassionate.

William’s wisdom and intellect, as well as his powers of deduction, lead him to uncover further details about the mysterious deaths in the abbey. With the help of Severinus of Sankt Wendel, the wise herbalist, William discovers evidence that Venantius was poisoned. Other clues seem to be pointing William towards the library, and he begins his quest in the scriptorium, in order to see what the dead scholar was reading. Later, he discovers that Venantius’s desk has been ransacked and a book is missing. William and Adso pursue this missing book for the remainder of the novel, for they believe it holds the key to the murderer’s identity.

The mystery deepens on the fourth day, when the missing Berengar is found drowned in a bath tub. This section is the exact midpoint of the novel, and thus it is significant that the Emperor’s theologians and the papal delegation arrive to begin their negotiations. Travelling with the Pope’s representatives is the notorious inquisitor, Bernard Gui, whom the novel sets up in an explicit contrast with William: William is wise, Gui is brutal. As the novel progresses, readers wonder who will gain the upper hand. As a representative of the Inquisition, Bernard is authorized to take over the investigation from William. He begins interrogating the abbey’s servants and other laypeople, sowing terror wherever he goes. There is a stark contrast between Gui’s brutal methods and William’s reliance on empiricism: Gui uses fear, William employs reason. The fourth section closes with the arrest of the peasant girl whom Adso loves; although she is innocent, she will be burned as a witch. The Inquisition’s worldview triumphs here.

The fifth day opens with the trial of Remigio, the cellarer, whom Bernard Gui suspects is the murderer, due to the monk’s checkered past and his association with a notorious heretic. Remigio’s associate, Salvatore, has already been tortured by Gui’s men, and has revealed all. Remigio ultimately cracks, too, and admits his past misdeeds. When threatened with torture, he confesses to the recent murders as well, but it is clear Bernard has the wrong man. It is unclear whether Bernard really cares who the real guilty party is; but as long as he has a prisoner, he is satisfied. The novel thus continues to question the nature and function of authority, including the power of the Inquisition, the authority of the Emperor, and the integrity of the Pope as Christ’s representative on earth. Corruption appears to be rampant in this world, and the fifth day draws to a close with the murder of Severinus. The visitors and the residents of the abbey are then subjected to a torturous sermon by Jorge, who warns that the Antichrist is coming and that they are all doomed sinners.

The sixth day opens on an even more ominous note: Malachi, the librarian, is missing. He reappears at morning prayers, where he suddenly slumps to the floor and dies. Instead of appointing a new librarian, the abbot clamps down. With a sense of increasing doom, William intensifies his investigation. He visits the treasure crypt to interrogate Nicholas of Morimondo, the glazier, who has now also been made the cellarer, due to Remigio’s arrest. From Nicholas, William learns that the abbey’s rivalries center around the powerful post of librarian; he also learns that whoever is appointed to this post is traditionally next in line to become abbot. This news gives William a new angle from which to pursue his investigation. No one is above suspicion, even the abbot himself. William formulates his new theory about the murderer’s identity and then heads to the scriptorium to look for evidence.

Meanwhile, the abbot is furious that William has failed to solve the mystery of the murders. He is even more furious that the Inquisition has gotten involved in the affairs of the abbey, which diminishes his own power and authority. When William asks too many questions about the abbey’s past, Abo dismisses him: William is told to leave the abbey in the morning. The abbot then sends everyone to bed. The atmosphere is tense: everyone is waiting for the murderer to strike again. At the very end of the sixth day, as night falls and the seventh day begins, William and Adso finally penetrate the most secret room of the library, the finis Africae.

In the forbidden room, Jorge is waiting for them. He is the mastermind behind all of the murders. He has been controlling the library for over forty years, first as librarian, and then, when he became blind, by controlling whoever was appointed librarian. In this way, he was able to bend Malachi to his will. William confronts Jorge and demands that he free his next victim, the abbot himself, whom Jorge has lured to the library. Jorge refuses, and the abbot suffocates in the stairwell in which Jorge has trapped him. William then demands the missing book, which he has now realized is the second book of Aristotle’s Poetics. The second part of this renowned work—in which the philosopher discusses laughter and the virtues of comedy—has been lost for centuries. This book is dangerous, Jorge says, but he allows William to look at it. Then, when William confronts him with his crimes, Jorge insists he has not killed anyone: they died because of their own sins.

Jorge is telling the literal truth: no one has died by his hand. Berengar used the secret of the finis Africae to persuade Adelmo to have sex with him. Adelmo, horrorstruck, kills himself, but not before confessing his sins to Jorge. In order to punish anyone who seeks out the forbidden book, Jorge rubs poisons on its pages. It is then stolen by the curious Venantius, who succumbs to the poison. Berengar finds Venantius’s corpse, and, fearing exposure, dumps the body in the vat of pig’s blood. Then he reads the book himself and is also poisoned. Jorge asks Malachi to retrieve the book, which Berengar had stashed in the infirmary. While doing so, Malachi murders Severinus at Jorge’s instigation. Then Malachi succumbs to curiosity and is also poisoned. Jorge believes that all of the deaths are divine justice, and is unrepentant.

Jorge now plans one final death: his own. In order to prevent the book from ever seeing the light of day, he starts ripping it apart and eating it. He will soon die from the poison, and thus his mission will be fulfilled. William and Adso attempt to stop Jorge, and in the ensuing struggle, Jorge throws their lamp on the ground and a fire breaks out. Then he throws the second book of Aristotle’s Poetics onto the flames, where it is lost forever. The library itself goes up in flames, and the fire eventually engulfs the entire abbey. William and Adso flee, and when they arrive in Munich, Adso bids his beloved master farewell. The time has come for him to take his holy orders. He never sees William again, but he will never forget the events of these seven days. As an older man, his own abbot sends him on a trip through Italy, and Adso “cannot resist” visiting the ruins of the now-abandoned abbey. He rescues bits of ruined books, and fashions “a kind of lesser library,” which he spends years lovingly deciphering and reading.

The novel ends with Adso as a very old man, near the end of his life, leaving us his manuscript. Indeed, he has carried “these pages”—the text of the novel—with him throughout his life, and he has “often consulted them like an oracle.” He is unsure who will find it, and whether there is any meaning or message to be found in the manuscript. In this ambivalent—and ambiguous—ending, Eco leaves us with the conundrum: what is meaning? How is meaning derived? The Name of the Rose will not provide answers, only questions.