When Charlotte goes to warn Piers about her match-making mother and they are trapped in a compromising situation because of another couple, the resulting mystery is a wonderful romp. Charlotte and Piers are an amusing, lovable couple. Piers is very self-contained while Charlotte is open and intelligent. When she decides to help him in his work (he's a government spy), all hell breaks loose. 
 I love that Piers lets Charlotte be herself since that isn't really his personality. This was a fun book to read and I love the way it all worked out.