Protagonist, Severian (who narrates this story), barely surviving a swim in the River Gyoll. Severian is at this point an apprentice belonging to the torturers' guild. Severian now heads for the Citadel the home of the tortures guild. Severian and a couple of apprentices decide to go to necropolis. There, he first meets Vodalus a legendary revolutionary. Vodalus is grave robbing until they are discovered by guards and a fight ensues. Severian steps in and saves Vodalus life earning a single gold coin as a sign of trust from Vodalus.
A short time passes and Severian gets prompted to a journeyman on the Feast of Holy Katherine. He then falls in love with a woman named Thelca, who is of a higher social status providing her with more liberties.
Thecla is unfortunately put forward to torture, Severian pities her and smuggles her a knife to commit suicide, doing so he breaks his guild's oath. Severian expects to be tortured but is instead moved to Thrax a faraway city in need of an executioner.
Master Palaemon gives Severian a letter of introduction to the city and Terminus Est, an outstanding executioner's sword. He departs the guild headquarters, traveling through the city of Nessus.
On his way there he meets Dr Talos and Baldanders in an inn. They are both travelling tricksters who offer Severian to join them in a play. Dr. Talos also manages to recruit a waitress to assist in this play.
Severian however, parts with the group beforehand and stops at a rag shop to buy a mantle, in order to cover up his uniform guild. The shop is owned by a brother (Agilus) and sister (Agia) who want to purchase Terminus Est, to which Severian refuses. Shortly after a masked man enters the shop challenging Severian to a duel to which he accepts. In order to duel Severian needs to secure an avern a deadly plant used for duelling, Agia agrees to accompany him.
They reach the Botanic Gardens where Severian accidently falls into a lake used to inter the dead. There he finds a woman named Dorcas and the two surface together. The three now travel to an inn where when eating dinner Severian receives a note warning him about one of his companions.
The duel now begins and Severian is wounded by the avern, he somehow survives this and wins the duel. Finding out however, his opponent was Agilus. The next day Severian is tasked with executing a person, this turns out to be Agilus to whom he does execute. Later Severian and Dorcas begin to travel they meet Dr Talos again who is ready to perform his play. Severian assists them in this act and they now form a group who set out to travel towards beyond the great wall of Nessus.