Traitor`s Gate features Thomas much more prominently than Charlotte. Thomas` surrogate father, Sir Arthur Desmond, the owner of the estate for which Thomas` actual father was the gamekeeper, has died in his club in London. The death is ruled accidental, or suicide, but his son Matthew, Thomas` close boyhood friend, is convinced it must have been murder, and asks Thomas to investigate.
Thomas is unable to officially investigate Desmond`s death, but rather fortuitously he is asked to investigate a case of missing information at the Colonial Office, to do with Africa and with British support for Cecil Rhodes. As it turns out, Arthur Desmond, formerly employed in the Foreign Office, had just prior to his death been making "wild" accusations of abuse of power in the government support of Rhodes. Naturally, Desmond`s death and the missing information are linked, and, more importantly, both are linked to the mysterious organization Thomas has run afoul of in previous books, The Inner Circle.
As Pitt`s investigations continue, his own life and Matthew`s are threatened, another murder is committed, and finally Pitt`s discoveries trigger a chain reaction of suicides and murders, ending somewhat in medias res with Pitt apparently ready to openly take on the Inner Circle.
The story is entertaining, and the solutions to the crimes are reasonably clever and interesting. However I don`t rank this as highly as the best books in the series for a few reasons. The Inner Circle has become non-credible to me, in its villainy, and its apparent size and power, not to say the incompetence of such a powerful organization in dealing with such a minor figure as Pitt. Pitt`s solutions to the crimes take on the all-too-familiar form of confronting the criminal with the (often rather sparse) evidence of his wrongdoing, upon which he either confesses or commits suicide. The device of having Pitt assigned to investigate a case of espionage is rather unconvincing. Also, the key crime of the book (the second murder) is not only difficult to credit as far as motive is concerned, but is committed in a foolish manner which seems calculated to ultimately draw attention to the murderer (indeed Thomas is misled rather more than I think he should be).
Finally, a key element of the enjoyment of this series is the ongoing stories of the advancing social life of the continuing characters. The books generally feature a love story or two, and this is no exception, but I didn`t find the love stories very involving. And as I said, Charlotte`s role in this book is minor, which is understandable for this book, but something of a drawback nonetheless.