A burning fog drifts over England in summer 1783 sickening and killing those exposed. Dr. Thomas Silkstone, a colonist transplanted to London, is in the country visiting his fiance Lady Lydia Farrell when the deadly fog hits. A scientist at heart, Silkstone studies the phenomenon and tries to devise treatments.
At the same time, Lady Lydia learns the son she thought died in infancy - now six years old - is still alive. Anxious to find her son, Lydia and Thomas set out to look for him. Unfortunately, nefarious parties bent on controlling Lydia and choosing the heir to her estate are also on the trail of the boy.
Meanwhile, in the chaos of the deaths from 'fog disease' several murders occur. Victims include a married temptress, a corrupt estate steward, and a brother and sister accused of being possessed by the devil. Reverend George Lightfoot, whose wife succumbs to the illness, is sure God's wrath is responsible and preaches fire and brimstone (there's a little too much of this for me).
Though the historical atmosphere and characters are interesting, and the saga of Lydia and her son is compelling, I became bored with the book. For me it doesn't measure up as a mystery story. I've grown accustomed to modern detective stories with scads of forensic evidence, and in this book the culprits are discovered as much by luck as anything else. To me this seems more like a historical novel than a historical mystery.