Half a Crown by Jo Walton

Jo Walton wraps up the series of Inspector Carmichael books, I think, with this one. She continues the device of having the story told from two POVs, in this case Carmichael's and his "niece" Elvira's. Elvira is actually the daughter of the his deceased sidekick, Royston, whom he has informally adopted and tried to provide with a proper education. Elvira is on the verge of coming out as a debutante and being presented to the Queen, as the story begins.

The fascists are in power pretty much everywhere, with the Japanese and Germans having won the war, and occupying vast spheres of influence. Jews are being persecuted openly even in England, with many of them being deported to The Continent, and England is about to open her own concentration camp to take advantage of their free labor.

Carmichael is now the commander of The Watch, a Gestapo-like organization responsible for rooting out dissenters and Jews. Unbeknownst to his superiors, he has formed a group he calls the Inner Watch, which has ties to the underground railroad which gets Jews and others out of England and off to Canada and Africa, where they can live without fear. He and his men in the Inner Watch have managed to help thousands escape over the past decade, and no one suspects a thing.

Elvira and her friend, Betsy, attend an Ironsides rally with a gentleman friend of Betsy's father, and enjoy the torchlit parade and humilation of captured Jews, up until the rally goes suddenly violent and turns into a riot. Elvira is arrested during the riot, and her "uncle's" enemies in the ordinary police force and at Scotland Yard decide to use her as a lever against him. Carmichael uses his position within the Watch to force them to release her, for a time.

Elvira hasn't any idea of Carmichael's subversive activities, but she does overhear a suspicious conversation between him and the woman who was responsible for getting our heroine from Farthing, Lucy, out of the country. When she is re-arrested later on, she lets this little bit of information slip, and Carmichael's former boss, Penn-Barkis, believes he can bring Carmichael to heel. Things get twisty and dangerous, as all of the different players work out their own intrigues, but the conclusion is satisfactory, for the first time in this whole series.