This is part of the Flavia de Luce series, which is lovely. The detective is an 11 year old girl with a love of chemistry and the series is set in 1950s England.
An ongoing theme throughout these books has been the effect of the loss of their mother in a mountain climbing accident when Flavia was just a baby.
At the end of the previous book, Flavia’s mother had been found. The implication was that perhaps she’d survived the accident, but no. Not so much.
This book has far less traditional mystery elements. There is a suspicious death, on the train platform when the body returns home ceremoniously, and a mysterious comment from Winston Churchill, attending the body home, but the main thrust of this book is unravelling the mystery of Harriet de Luce. Was she a spy during the war? Why did she leave her newborn to go mountain climbing?
These books are completely charming and I highly recommend them but I do not recommend starting here. Go back and read the first one, “The Sweetness at the Bottom of the Pie.” I would be truly surprised if you don’t get hooked on these.
I feel like I should write more here but there’s not much more I can say without revealing plot elements. Sorry!