Lord Marsdon worked for the Home Office (he was a spy for England). Elizabeth and John Trent were also spies for England. They had just come from France. Elizabeth' s sister Louisa was visiting with them. Louisa was more proficient with a gun than Marsdon. They were threatened by Frenchmen as there were bounties on Elizabeth and John. Louise rescued Marsdon when he was overcome by the thug. She fainted when she blood though. While there Marsdon fell in love but he had 3 sister's to marry off first. However Louisa could not wait that long as her grandfather the Duke of Danby expected her to marry before Christmas.
They saw one another at the balls where he escorted his sister's. Jordan Trent escorting Louisa. Marsden was seeing red. His sister's were helping Louisa. It was quite interesting. This precedes the novellas of his sister's finding their mates. You may want to read those after this one.