What's the Name of That Book??? discussion

This topic is about
The Dress Lodger
SOLVED: Adult Fiction
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SOLVED. Historical Fiction, Blue Dress, Plague in Europe, Prostitute with fancy blue dress and infant son with bizarre heart condition [s]
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I remember the title as being "the blue dress" but I can't find it.
It takes place during a major illness, I think the plague, in old Europe. A young woman is a prostitute living in a poorhouse, but she has a very fancy blue dress that wins her lots of clients on the street. She has an infant son with a strange heart condition (his heart is out of his body?) and a scientist/doctor is desperate to steal the child to study him. I think the scientist/doctor is chased by a mob at one point for grave-robbing.
Lots of interesting historical details that stick out in my mind: one of the other poorhouse tenants had a job as a matchmaker, and she glowed slightly from the phosphorous. The poorhouse doesn't have any working windows because of a window tax. The bartender doesn't wash the drinking glasses, but wipes one 'clean' if the incoming customer is important.
It was a wonderfully atmospheric novel and I wish I could find it again. Thanks in advance for any help!