India Black and the gentleman thief

"India Black's double life operating a high-class brothel and running high-stakes espionage for Her Majesty's government can take its toll. But there's no rest for the weary-particularly when an international conspiracy comes knocking; India Black is one of Victorian London's most respected madams-not a bloody postmistress. So when Colonel Francis Mayhew forwards a seemingly innocuous shipping bill to her address, she's puzzled. And when three thugs bust down her door, steal the envelope, and rough up both her and fellow agent Frence;well, that's enough to make India Black see red. The veteran spies soon discover that Mayhew has been butchered in his own bedroom. An impromptu investigation leads them to London's docks, where India makes a startling discovery she can't bear to tell the rakish French-she has a history with their chief suspect, the gentleman thief who once stole her heart; "--

Spy for Queen Victoria, India Black, disguises herself as a servant to protect Her Highness from a possible assassination attempt by Scottish nationalists while spending the Christmas holidays in Balmoral.