The year is 1803 and England and France are bickering. Napoleon is hoping to break the English, so he supports a group of Irish rebels in uprisings against them. To help with this, the Black Tulip, France's most deadly spy, has arrived in Ireland. Also in the same area is England's best spy, the Pink Carnation. Back in England, Letty Alsworthy is oblivious to anything dealing with Napoleon, spies or espionage. Soon, with no warning, she will be thrust into the middle of it all.

It's midnight in England and the only thing on Letty's mind is putting a stop to the elopement between her older sister Mary and Geoffrey Pinchingdale-Snipe (second in command of the League of the Purple Gentian). In her attempt to save her sister from shame, Letty and Geoffrey are caught in a compromising position and forced into marriage. Even before the wedding guests leave, Geoffrey mysteriously departs for Ireland to see about a horse. Letty decides to board a ship to Ireland to find her husband and explain that she did not trick him into the marriage. What she uncovers could put both of their lives in danger.

Letty dons dark clothing and travels as the widow Mrs. Alsdale. Not long after her arrival, she runs into her husband at a party. Neither one realizes they are both "undercover" and it gets tricky when someone recognizes Letty from her wedding. Geoffrey reluctantly explains to Letty what he secretly does, and against his better judgment, enlists her help with the mission. During their assignment, they begin to fall in love. As people they know are murdered, Geoffrey wants nothing more than to complete the mission and get back to England with Letty.

THE DECEPTION OF THE EMERALD RING is the third book in Ms. Willig's Pink Carnation series. Throughout the book, Willig intersperses the findings of present-day researcher Eloise Kelly as she researches for her dissertation about Geoff, Letty, the Black Tulip and numerous others, while at the same time she hopes that Colin Selwick (descendent of Henrietta Selwick Dorrington) will ask her out. Although I haven't read the first two books, THE SECRET OF THE PINK CARNATION and THE MASQUE OF THE BLACK TULIP, I found that THE DECEPTION OF THE EMERALD RING stands well on its own. I plan on reading the first two and cannot wait for the fourth book.