An Old Betrayal (Minotaur), the seventh Charles Lenox mystery by Charles Finch, makes pleasant reading. This is a much better novel than A Death in the Small Hours, which I reviewed a few weeks ago after it came out in paperback.
Finch doesn't write pulse-pounding thrillers. His books are more low-key, more cerebral. Sometimes they can get a bit dull, as in the case of the previous book, but An Old Betrayal doesn't have that problem. The tale begins when Lenox, now a Member of Parliament and apparently out of the detective business, fills in for his protege, John Dallington, who is sick in bed. Dallington has received a note from a prospective client with a striped umbrella, whom the detective is supposed to meet in a cafe. Lenox goes in his place, but expecting to meet a man, pays little attention to the only person there with a striped umbrella, a young woman. The early chapters are taken up with trying to find this woman to discover what her problem may be. Her note suggests to Lenox that she may be in some danger.
It turns out that the woman is not the only one in danger. A series of murders follows, as does as threat against Queen Victoria's palace and, perhaps, the queen herself.
A couple of intriguing subplots add to the pleasure of this novel. Rumors are circulating in high places that Graham, his long-time secretary and aide, cannot by trusted, and Lenox finds his political career in jeopardy as a result. Then a mysterious lady detective opens a new agency that promises to use more modern and scientific investigative techniques than Lenox and Dallington have been using. This poses a threat of a different kind.
The plot gets complicated, as they often do in good mysteries, but it's fun watching Charles Lenox sort it all out.