In This Grave Hour (Maisie Dobbs #13) by Jacqueline Winspear; 2018; Softcover.

Sunday September 3rd 1939. At the moment Prime Minister Neville Chamberlain broadcasts to the nation Britain's declaration of war with Germany, a senior Secret Service agent breaks into Maisie Dobbs' flat to await her return. Dr. Francesca Thomas has an urgent assignment for Maisie: to find the killer of a man who escaped occupied Belgium as a boy, some twenty-three years earlier during the Great War. In a London shadowed by barrage balloons, bomb shelters and the threat of invasion, within days another former Belgian refugee is found murdered. And as Maisie delves deeper into the killings of the dispossessed from the "last war," a new kind of refugee -- an evacuee from London -- appears in Maisie's life. The little girl billeted at Maisie's home in Kent does not, or cannot, speak, and the authorities do not know who the child belongs to or who might have put her on the "Operation Pied Piper" evacuee train. They know only that her name is Anna. As Maisie's search for the killer escalates, the country braces for what is to come. Britain is approaching its gravest hour -- and Maisie could be nearing a crossroads of her own.