In the late 19th century, the British Empire has become a global power. Due to the strict class stratification, the average citizen has little chance of successfully rising up to the top, where the despicable nobility rules over them all.
The first son of Earl Moriarty, Albert Moriarty finds two orphans, Louis and his unnamed brother, that share a common hatred for the corrupt British nobility and adopts them as his brothers. They scheme together to kill Albert's cruel biological brother William, burn down the family estate, and start a new life together using illegal means to destroy the class system and Louis's elder brother takes William's name and identity.
While enacting an elaborate scheme to murder a noble who was hunting commoners, William encounters Sherlock Holmes, who deduces a third party was involved in the murder. This piques William's interest in Sherlock, leading him to test his abilities by framing Sherlock for murder.
Thus ensues a battle of wits between two of the greatest minds the world has ever seen as William relentlessly pursues a better world and Sherlock pursues the reason why he was chosen by the infamous Lord of Crime to play a part in his murders.