What if Sherlock Holmes had a female apprentice? This book explores that possibility. Mary Russell, or simply Russell to Holmes, is a highly intelligent young woman full of ambition and attitude. Holmes, although retired from the world of detective work, sees a lot of potential in Mary and decides to teach her the art of sleuthing. Friendship and eventually love for one another grows within teacher and apprentice as they experience the hardships and rewards of a sleuthing partnership.