In some ways, this is a better book than my rating would suggest, but I didn't enjoy it nearly as much as many other Baloghs.
The first one-third or so takes place in Brussels before the Battle of Waterloo. Ellen Simpson is happily married to Charlie and has been "following the drum" for five years. We know, just from the book blurb, that Charlie will die, but they are so happy, and their scenes together are so sweet, that it's hard to read.
Our soon-to-be hero, Dominic, is Charlie's best friend, and after Charlie dies, Ellen nurses a severely wounded Dominic back to health. They have a passionate one-week affair, but then Ellen suddenly decides that she's being unfaithful to Charlie by not mourning him longer. She's ashamed of her conduct and sends Dominic away.
The rest of the story finds everyone back in England, where Ellen hates Dom but secretly still loves him. And Dom loves her, but that's a secret too. And everybody knows that Ellen's expected baby was fathered by Dom and not Charlie, but nobody seems to mind or even give it much of a second thought.
There's a houseparty with lots of people, most of whom seem superfluous to the plot. It all just didn't work for me.
The Earl and Countess of Amberly appear frequently in this book, and I liked them a lot. Perhaps I'll go back and read their story in The Gilded Web.