This is book number 4 in the Sherlock Holmes and Lucy James Mysteries series.
A young American actress arrives in London hoping to learn her identity, just as Sherlock Holmes is closing in on a master criminal. Their worlds collide, and not even Holmes could have foreseen the impact
This novella is the prequel to The Sherlock Holmes and Lucy James Mystery series. It takes place three days before the opening of The Last Moriarty.
The optimal reading order of the Sherlock and Lucy books is:
The Crown Jewel Mystery
The Last Moriarty
The Wilhelm Conspiracy