June 1946. London, England. A murdered man. A mysterious woman. A note in another language. Irene Holmes, daughter of the long-retired Sherlock Holmes, used her unique talents of deduction and observation to assist her childhood friend Detective Eddy Lestrade with his cases during the war. With the war over, Eddy keeps her on as a consultant, finding her essential to solving crimes. During one of these cases, Irene meets Joe, a man who finds her instantly intriguing and has enough opinions of his own to keep up with her challenging personality. When Eddy requests her help on a perplexing murder case, Irene drags Joe along as her assistant. Using many of her father's lessons, they traverse post-war London, determined to find the killer before he strikes again.