London, 1781. Harriet Westerman anxiously awaits news of her husband, a ship's captain who has been gravely injured in the king's naval battles with France. As London's streets seethe with rumor, a body is dragged from the murky waters of the Thames.

Having gained a measure of fame as amateur detectives for unraveling the mysteries of Thornleigh Hall, the indomitable Mrs. Westerman and her reclusive sidekick, anatomist Gabriel Crowther, are once again called on to investigate. In this intricate novel, Harriet and Gabriel will discover that this is no ordinary drowning-the victim is part of a plot to betray England's most precious secrets.