A Most Discreet Inquiry by Cheryl Bolen

It all started quite innocently when Lady Daphne Chalmers's duchess sister came to her sleuthing sibling for help in retrieving love letters she wrote to Major Styles, now deceased. But as Daphne and her own lover, Captain Jack Dryden of His Majesty's Hussars, join forces to track down the letters, they follow a trail of treachery and murder that threatens the entire kingdom.
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What critics are saying about The Regent Mysteries:
A delightful blend of humor, romance, and mystery, a romp through Regency society, sprinkled with appealing characters and colorful figures from British history." - In Print