In this book, Frank Emerson has uncovered a previously lost narrative by Dr. John H. Watson that illustrates how he and Sherlock Holmes, working in tandem with Detective Chief Inspector Frederick Abberline of Scotland Yard, conducted an intense 15 year investigation and pursuit that culminated with the unmasking, arrest, trial, and ultimate execution of the real Jack the Ripper.

From some clear pieces of glass and a raven's feather, the great detective must divine exactly who the client was and what prompted him to seek assistance at 221B. Fortunately, Holmes has a number of experts upon whom he can rely as well as his own vast store of esoteric knowledge. Treading a twisted path, Holmes soon finds himself matching wits with an unseen criminal, who appears to be the equal of the late Professor Moriarty. At the same time, he is tasked with sparing the monarchy any possible embarrassment that may stem from the investigation.

For all we know, or think we know, about Sherlock Holmes and Doctor Watson, what we don’t know is far, far greater. In the duo’s first case, A Study in Scarlet, we learn that Holmes and Watson met on January 1st, 1881, and subsequently moved into an apartment together at 221b Baker Street. Their first case officially began on March 4th of that year, and it is argued that “The Adventure of the Resident Patient” possibly took place in October of 1881, depending on which version of the story you read. But what happened during the rest of 1881? Or all of 1882?

1896. A new client at Baker Street claims he’s being threatened via the new art of the moving image. Eadweard Muybridge, pioneer of motion picture projection, believes his life is in danger. Twice he has been almost run down in the street by the same mysterious carriage, and moreover, disturbing alterations have been made to his lecture slides. These are closely guarded, yet just before each lecture an unknown hand has defaced images depicting Muybridge himself, which he has discovered, to his horror, only as he projects them to his audience.

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".