Summary from Goodreads:
London's social season is in full swing, and Victorian aristocracy is atwitter over a certain gentleman who claims to be the direct descendant of Louis XVI and Marie Antoinette. Adding to their fascination with all things French, an audacious cat burglar is systematically stealing valuable items that once belonged to the ill–fated queen.
But things take a dark turn. The owner of one of the pilfered treasures is found murdered after the theft is reported in the newspapers, and the mysterious thief develops a twisted obsession with Lady Emily Ashton. It takes all of Lady Emily's wit and perseverance to unmask her stalker and ferret out the murderer, while faced with a brewing scandal that threatens both her reputation and her romance with the dashing Colin Hargreaves.
Coming back to Lady Emily, I was delighted to find that her second mystery is more streamlined than the first. Emily is determined to be her own person - she and Colin Hargreaves seem to be progressing in their romance but she won't be bullied into marriage (by her social-climbing mother) or deterred from intellectual pursuits. Although Colin is a master spy, Emily doesn't expect him to swoop in and rescue her when her investigations become dangerous. Very enjoyable.
Dear FTC: I read a copy purchased on my Nook.