In This Grave Hour is the most recent "Maisie Dobbs" historical mystery, and about the dozenth or so in the series. This series began when it was 1929, and Miss Dobbs was first opening her detective agency in a quiet London square. It is now September 1939, Britain is at war with Germany, and Maisie has a new case - is someone murdering men who were refugees from Belgium when they were boys, 25 years ago?
Matters are complicated by her father having 3 child evacuees living with him down in the country - two boys whom he can handle, and a five-year-old girl who won't talk. An additional problem is that no one seems to know her name, who her parents are, or where she's from.
Maisie will investigate both cases, and come to suspect that her client is either lying to her, or not telling the entire truth.
This was a distinct improvement from the last one, Journey to Munich, which featured spies and Americans ex machina.