Franciscan friar William of Baskerville and Adso of Melk, a Benedictine novice travelling under his protection, arrive at a Benedictine monastery in Northern Italy to attend a theological disputation. Upon their coming, the monastery is disturbed by a suicide. As the story unfolds, several other monks die under mysterious circumstances. William is tasked by the monastery's abbot to investigate the deaths, and fresh clues with each murder victim lead William to dead ends and new clues.
The protagonists explore a labyrinthine medieval library, discuss the subversive power of laughter, and come face to face with the Inquisition, a reaction to the Waldensians, a heresy which started in the 12th century and claimed to advocate an adherence to the Gospel as taught by Jesus and his disciples. William's innate curiosity and highly developed powers of logic and deduction provide the keys to unraveling the abbey's mysteries.