Young Adso denounces the hedonistic ways of his influential father and joins the enlightened friar, William of Baskerville, as his new apprentice. They arrive at an abbey for an important theological debate but a strange death occurs.

After another suspicious death, William and Adso look for a way to get into the abbey's mysterious library. Meanwhile, inquisitor Bernardo Gui, who's traveling to the abbey, brings the wrath of god to all he deems sinners along the way.

A monk goes missing, William looks for a new pair of glasses to inspect the library's books, Adso falls for a free-spirited peasant girl, huntress Anna goes on a mission to avenge her family and kill Gui.

The peasant girl finds wounded Anna, Gui looks for allies and foes in the abbey, Adso breaks his vows, William debates comedy, the main debate about apostolic poverty turns violent, perverted monk Salvatore captures the peasant girl.

Anna infiltrates the abbey to find her old ally Remigio, William takes part in the main debate but another murder interrupts it, Gui arrests Remigio for the crime despite William's doubts, Adso tries to rescue the peasant girl.

Gui uses Salvatore to get to Remigio and put him on trial, William gives his thoughts on both the show trial and the poverty debate between the Franciscans and the Church, Anna tries to rescue her friends, another mysterious death occurs.

With the debate over, Gui condemns Remigio and the girl to be burnt at the stake, William and Adso try to solve the library's puzzle and catch the killer before it's too late, and Anna makes her final desperate move.