I remember when I read the last book in this series, The Chalmers Case, that I felt it lacked focus and rambled a lot.   I'm happy to say this one was a lot better; just one main mystery and one small mystery, all told succinctly and without filler.  And that's what I enjoy about this series; the fact that a well-written mystery doesn't need a dead body, a lot of characters and and an excess of plot threads.