The fifth book in Sulari Gentill's Rowland Sinclair series is set in England in 1933 after Rowland and his friends have escaped from Germany. In London Rowland and his brother visit Lord Pierrepont in the hope that they could persuade someone in the British government to listen to Rowland's story about atrocities occurring in Nazi Germany. Unfortunately when they arrive at his rooms they discover that he is dead and his niece who also acts as his assistant is suspected of murdering her uncle. Rowland and his friends attempt to prove the innocence of Allie Dawe and in so doing find themselves in a world of spies and that their lives are in danger. The book is set in London in the time when appeasement with the Germans was paramount. As with her first book Gentill weaves a fictional story with historical fact providing an outline of mistrust and events occurring in the 1930s.
I have not read numbers 2 to 4 in this series but it was still possible to follow the plot, however it probably would be a fuller reading experience to read all the books in the series as published in sequence in order to fully follow the story.