When the novel begins, Francis is a 17-year-old novice at the Albertian abbey. He is devoted to his vocation but finds his vigil in the desert dreary. His encounter with the wandering old man leads to various expressions of his curious temperament and intolerance for pressure. He finds himself at the center of a controversy for which he is unprepared.

Francis is long-suffering and dutiful, as befits his station as a novice for an abbey. He also represents curiosity and an appreciation for artistic endeavors, as he shows during his investigation of the fallout shelter and his dedication to the lambskin illumination and the blueprints of Leibowitz. As the one who brings the story about the old wanderer into the abbey, Francis also symbolizes the ease with which stories can mutate into grander, uncontrollable narratives.

Taddeo is a renowned young scholar with a brilliant mind and a secular outlook. His name is already mentioned in the same breath as other revered academics and theologians. Taddeo is legitimately curious and devoted to scientific progress, but he is also prideful and ambitious. He is professionally frustrated when he witnesses the success of the dynamo since he will not be the one to discover it.