Narrated by acclaimed British actor Edward Petherbridge, The Last Moriarty is set in London, 1895. On a cold November morning, a young American actress visits 221B Baker Street, desperate for Sherlock Holmes to protect her from the threats of a mysterious, menacing man who has recently appeared in her life. Holmes agrees to help, even though he has just promised the Prime Minister to solve the murder of John D. Rockefeller's security agent before the incident can derail an upcoming British-American summit.

She's an unconventional lady who has traveled the world, practices the art of self-defense most excellently, and has an interesting tattoo in—ahem—a very unusual place. He's a former member of the Metropolitan Police, now a private investigator, who grew up on the poverty-ridden streets of Edinburgh and has worked the dangerous back alleys of London's notorious East End. A vicious murder brings them together in a race against time that takes them from the sordid back streets of London into the elite private clubs of the powerful and rich.

The Western Front, 1915. It's been 20 years since Becky and Flynn first met, in the adventures recorded in the Sherlock and Lucy Mystery Series. Now they're fighting for England in the Great War. But they still have an incomparable ally in the great detective himself.

A murdered opera singer. A duke drenched in her blood. For Bow Street Officer Hugh Marsden, the brutal killing is a straightforward case. Ever since his exile from polite society, the chance to arrest a high and mighty peer of the realm has never presented itself. Hugh won't snub the opportunity now. But Audrey Sinclair, the Duchess of Fournier, is certain her husband is wrongly accused, and she's determined to prove it to the arrogant Bow Street officer, even if she must employ her most peculiar ability—or perhaps curse—to guide her investigation. After all, a duchess can do as she pleases.

Hours later, the man’s cold body lies in the city mortuary, alongside the woman he couldn’t save. And his sister, unconventional nurse Gemma Tate, tracks down troubled police inspector Sebastian Bell to unravel the truth. Sebastian has enough pressure to solve the murder of an aristocratic heiress without Gemma meddling in his case. But the cryptic sentences she brings him from her brother’s notebook could be a crucial lead. If only they knew what “milky way” meant.