This book moves away from The Devil in Green and there is no mention of Mallory and Sophie, the new Brothers & Sisters of Dragons. Instead it seems to start off at a complete tangent with a plague now affecting humanity and the struggles of a single country doctor called Caitlin Shepherd. On a search for some kind of treatment or cure Caitlin crosses into the Celtic otherworld were she is aided by The Morrigan and then the action does speed up, if at times a little rushed.
Anyone reading these trilogies will, as I did, think this is a disappointing book, that is too far removed from the beloved if flawed characters in The Age of Misrule books. But trust me on this, having now read the series, this book is a bridge between the original five Brothers and Sisters of Dragons and all those who will follow.
To give just a little tease, we do meet up with the original five again but to say anymore would be a spoiler.
In the last of the Dark Age books, "The Hounds of Avalon" it all starts to come into focus but the whole complex story becomes much more clear in the first of the next trilogy "Jack of Ravens".
So although I didn't think of this book as the best in the series I do think it was, if a bit less polished than the four previous, necessary and perhaps important to set the basis for the last trilogy.