This is a book where the main character, in the start, is in the sewers, I think, and there are feral children called ‘sewer rats’ chasing him? I think, it was because he was trying to save a cat? There is a cave-in and the cat appears to be someones familiar or something because it goes and brings back help. The main character wakes up and I think I remember they were giving him a honey bath or something to combat severe dehydration. I think the people who rescued him brought him to a group that were luddites. The main character turns out to be an empath and at some point lets his shields down outside and because there is a plague in the area he is overwhelmed by the suffering around him. His romantic interest is named Mary? She is one of the luddites and helps him when he becomes overwhelmed. At some point they try to help capture and rescue the feral children, these feral children turn on anyone that reaches a certain age. The main character was traveling through the sewers in the beginning because of his empathy, it was quieter down there.