Charlotte Sapori has led a wonderful life, safely tucked in the bosom of her family. Her mother, Irene Adler, is a renowned opera singer, while her father, Lucca Sapori, does important government work that frequently takes him away from them. Charlotte is close to her older brother, Nicco, and they are both doted on by their parents. All is well until her mother receives an unexpected diagnosis which shakes the family to its core.

Knowing herself to be dying, Adler confesses to Charlotte things that have long been kept from her, telling her to find and read her diary. A distressed Lucca Sapori tells his daughter to read his as well. And by the way, Lucca Sapori is not his real name. In fact, she may have heard of him—he is actually the world-famous detective, Sherlock Holmes.

Charlotte finds both diaries and plunges into the hidden world of Irene Adler and Sherlock Holmes as she discovers what brought them together, and how they managed to stay together for thirty years despite having to battle the odds.