Autumn is in the air as Lady Petra Forsyth and some of the most illustrious members descend upon Windsor Castle for a week of royal celebrations, with the highlight being Queen Charlotte’s inaugural patisserie contest. Her Majesty has requested that Petra herself serve as one of the judges. Yet upon arrival, Petra instead encounters a body of one of Her Majesty’s guests and to the valet still tugging at the silk ribbon used to strangle the victim, who turns out to be Oliver Beecham. But as Oliver is hauled away to the dungeons, he claims the late guest argued with several aristocrats about hiding a potentially scandalous document. When some poisoned tea meant for Petra is consumed by one of her fellow judges, it’s clear the real killer is still walking the castle’s halls. Indeed, Petra will need to act like a lady, eat like a chef and think like one of Her Majesty’s best spies before the celebrations turn deadly.

London may be cheering the news of Napoleon’s surrender at Waterloo, but Lady Petra Forsyth has little to celebrate after discovering that the death of her viscount fiancé three years earlier was murder. The man responsible is her secret paramour, Duncan Shawcross, yet the scoundrel has disappeared, leaving only a confusing riddle about long-forgotten memories in his wake. Meanwhile, Queen Charlotte has tasked Petra with attending an event at the Asylum for Female Orphans and making inquiries surrounding the death of the orphanage’s matron. There may be a link between the matron’s death and a group of radicals with ties to the aristocracy. Then Petra overhears a nefarious conversation with two other men about a plot to topple the monarchy, set to take place during three days of celebrations currently gripping London.

After losing her beloved fiancé in an accident three years earlier, Lady Petra Forsyth announces in front of London’s loosest lips that she will never marry. A woman of independent means, Petra sees no reason to cede her wealth and freedom to any man now that the love of her life is gone. Instead, she plans to continue enjoying the best of society without any expectations. But when ballroom gossip suggests that a longtime friend has died of a fit due to her “melancholia” while in the care of a questionable physician, Petra vows to use her status to dig deeper --- uncovering a private asylum where men pay to have their wives and daughters locked away, or worse. Just as Petra has reason to believe her friend is alive, a shocking murder proves that more danger is afoot than she thought.