Sherlock Holmes, legendary sleuth of Victorian London, is asked to authenticate the work of what appears to be a long-lost Shakespearean play. Alas, just as the famed detective is about to announce his conclusion, the manuscript is stolen. As Sherlock and his trusted sidekick, Dr. John Watson, begin to unravel the mystery of the missing play, their investigation leads them on a convoluted but logical path. But the closer they come to the missing play, the more their lives are endangered.

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.

When Mrs. Hudson asks Holmes and Watson to find a missing girl, neither men expected what they would find. Along with Lestrade, they are plunged into a case of abduction and murder. As they race from Marylebone, to Finchley, to Wapping, and back again, time is running out for them to solve the case without further casualties. With two of their own under threat, the pressure is mounting to catch and stop the group known as "Hellfire Heirs".

The world was not prepared for this story, a conspiracy hatched in the highest levels of the British government. A rogue Minister of Defense plans to turn soldiers into blood-thirsty animals—and Holmes and Watson may be among their first victims. The adventure starts when Holmes is warned away from investigating Jack the Ripper’s heinous crimes. Despite Holmes’ well-known skills, he is sidelined. He must content himself with a straightforward case, finding a bolting beau, the result of a simple lovers’ quarrel. But that “romance gone wrong” is really the key to a nasty secret.

Christmas morning 1902, London, England. A bottle of fine French wine from the Côte de Beaune region of France, intended as a gift from Mr. Sherlock Holmes to his old friend Dr. Watson, is found to have been drained of its aromatic spirits during the night and filled with sand. But not just any sand.