Brother Diaz is first dazzled by the Chapel of the Holy Expediency. The marble, paintings, saints, candles, and jeweled scriptures make Diaz imagine that he has finally been given a prestigious post, and Baptiste's irreverent conversation only partly interrupts that satisfaction. Diaz's hopes of comfort and status collapse when Jakob of Thorn slides the pulpit aside to reveal a hidden stair and tells Diaz that his true flock is kept below the chapel.

Baptiste leads Diaz downward through older and darker layers of the building, from finished masonry into ancient tunnels of cold seamless stone said to be the remains of the city built by the Witch Engineers of Carthage. Diaz notices Baptiste's many knives and grows steadily more alarmed. At a heavily warded door they meet Hobb, an English guard who says he "looks after the devils" and warns Diaz to stay back from the bars and trust nothing the prisoners say.

Inside the cells, Diaz meets the first of these "devils," Balthazar Sham Ivam Draxi, a naked magician in chains. Balthazar denounces the Church's distinction between Black Art and White as hypocrisy, while Baptiste and Jakob explain that Balthazar was convicted for dangerous acts, including corpse magic and bargaining with demons. Diaz learns that Balthazar has been stripped of clothing because even dirt and cloth might let him work spells, which shows Diaz that these captives are not merely oddities but serious threats.

In the next cells Diaz encounters Sunny, an elf whose mere presence unnerves him because he almost fails to notice her until she moves, and then Baron Rikard, a very old vampire whose polished manners are more dangerous than open violence. As Rikard speaks, Diaz is subtly drawn toward the bars and nearly offers himself within reach before Jakob snaps him back to his senses. The final occupied space is empty except for straw, scratches, and a slaughterhouse smell; Baptiste and Jakob explain that another member of the flock had to be moved because of intolerable behavior, and that the chapel's work causes constant turnover.

Shaken, Diaz admits that he has spent his life in monasteries and has no experience with anything like this hidden congregation of monsters and weapons. Baptiste and Jakob warn Diaz that the chapel is no place for rigid zeal, because a person who treats everything like a straightforward holy struggle will eventually break. When Diaz asks what happened to his predecessor, they explain that Mother Ferrara was faithful and zealous but too rigid for the pressures of the post, and Jakob ends the tour by bluntly confirming that she died.