This is book 3 of the Asylum for the Mechanically Insane. You MUST read this series in order. It is a serial and builds upon the previous books.
Dr. Granville and Viscount Somerly, his cousin, have created the gas that Lady Harbury uses to stay young. They have decided that they need money for themselves so they decide to set up a brothel and use the gas to enhance the sexual experiences of those frequenting this establishment. They make their arrangements but get more than they bargained for when they go into business.
Portia and Inspector Burke continue their investigations into the disappearances and deaths occurring at Harbury Hall. Portia has also told the inspector about the prisoners. In the course of her cleaning duties she has discovered old maps of Harbury Hall and comes up with what she believes is a viable plan to rescue the prisoners, especially the one with whom she has the strong connection. In order to avoid detection they need the services of Mrs. Howell, an antiquarian and amateur archeologist.
I like the heroes and heroines here. Mrs. Howell is interesting and brings a new way of looking at things to the story. Granville and Somerly are cads and bounders. A new doctor is introduced who may be able to handle Lord Harbury as he descends more into madness. Lady Harbury may be joining her husband on his journey to madness.
Portia does work on her plan to free the prisoners but it is barely mentioned. At the end things happen that did not make sense so I had to go back to see what I missed. Portia and her plan were very easy to overlook. Missing that causes confusion.
I am looking forward to book 4 which is not out yet. Ugh!!!!!!