When a mage of the Society of Trimegistus enters his shop, Lieth Alsander is in over his head. By offering a device for sale that would allow ordinary, non-magically-talented people to detect when magic is being used, he's come to the attention of the Society, and such attention is seldom good.

But Lady Carissa Sere hadn't come with threats of lawsuits or magical wrath. Instead, she offers Lieth a deal: in exchange for her protection and patronage, he’ll show his devices to her before offering them to the general public, and let her decide which are safe to develop, which are too dangerous, and which she wants to keep for herself.

Because Lieth isn’t the only one in danger. Her controversial politics have made Carissa enemies in the Society, particularly the leaders of the powerful War Party, and she hopes that Lieth and his devices will be an unexpected ace up her sleeve.

Working for Carissa brings Lieth face-to-face with her collection of shackles and cages and devices for causing pain or pleasure, and her mischievous acolyte Rown Telarch. It’s a hobby that Lieth finds fascinating and frightening in equal measure—but the more time he spends with Carissa, the more he finds himself longing to please her any way he can.