The Dead Cannot Hide — J.L. Buck

England, summer of 1812.

Lucien, Viscount Ware, a secret spy for the Crown, is asked by his grandmother to use his skills in locating a missing country girl. She had taken a governess's position near London almost a year ago and not been heard from for months. With the Prince Regent safely in Bath and Whitehall's attention on the war with Ameria, Lucien has the time and agrees to make a few inquiries.

The girl's employers tell him Lucy vanished one night ten months ago with all her belongings. Convinced there is more to the story, he obtains an invitation -- through his friend Lady Anne Ashburn -- to a houseparty in the neighborhood in order to continue his inquiries.

With the help of Lady Anne, the houseparty hosts, and others around the village of Blinkers Marsh, Lucien and his friend/fellow agent Sherbourne learn of a second missing girl, make a grisly discovery in a pond, and hear whispers of a deadly plot to unleash terror and disruption upon London.

They soon realize they are all in danger, along with hundreds or thousands of London citizens, perhaps the Crown itself -- and a wild race begins to unmasks the culprits and cut off the deadly plots before time runs out.