This series is a spinoff of the Bitter Thorns series. Although it may help understand the background, enough details are provided to enjoy the story if it hasn't been read.

Chloe is a healer who has moved to the mortal world to live with her brother, a fae, after losing their parents. She is mortal now since moving to the human realm.

Some of the villagers are starting to show odd symptoms. While working on gathering ingredients to make poultices for the ill, a fae from her past, Quintus, arrives asking Chloe to return with him to the fae realm. He informs her that mortals have invaded with iron, and the fae realm is in dire straits. Chloe declines the invitation, but when more villagers succumb to the sickness, she realizes that the only way to have any hope to save the mortal realm is to help the fae realm. Reluctantly, she agrees to return with Quintus to the fae realm in exchange for his help gathering ingredients.

Quintus transports Chloe to the fae realm after she falls into an icy river. She is stunned to see the state of the realm. How can she, a mortal, help save both the fae and the mortal worlds?

This book is gripping and so intense. I am looking forward to reading more in this series.