"Moriarty's Perfect Crime" is an anime series that reimagines the world of Arthur Conan Doyle's Sherlock Holmes stories, centering on William James Moriarty as the protagonist rather than the antagonist. Set in late 19th-century Britain, the story explores the rigid class system and societal inequalities of the era, with Moriarty positioning himself as a revolutionary figure aiming to dismantle the corrupt aristocracy.

William James Moriarty, a brilliant mathematician and professor, operates under the guise of a nobleman while secretly orchestrating elaborate schemes to eliminate corrupt figures within the upper class. He is aided by his adoptive brothers, Albert and Louis Moriarty, who share his vision of a more just society. Together, they form a clandestine organization that targets individuals who exploit their power and privilege, often framing their deaths as accidents or unsolvable crimes.

The narrative unfolds through a series of episodic arcs, each focusing on a specific target and the intricate plans devised to bring them down. Moriarty's methods are morally ambiguous, blending calculated manipulation with acts of violence, all justified by his belief in creating a better world. His actions eventually draw the attention of Sherlock Holmes, who becomes both an adversary and a foil to Moriarty's ideals. Holmes, portrayed as a genius detective with a sharp eye for detail, begins to unravel the patterns behind Moriarty's crimes, setting the stage for a cerebral battle of wits between the two.

The series delves into the backstories of its main characters, particularly William Moriarty, revealing his motivations and the trauma that shaped his worldview. Albert, the eldest Moriarty brother, serves as a political figure who supports William's plans from within the aristocracy, while Louis, the youngest, acts as a loyal enforcer and strategist. Other key characters include Fred Porlock, a skilled assassin allied with the Moriarty brothers, and Irene Adler, a cunning and resourceful woman who occasionally crosses paths with both Moriarty and Holmes.

As the story progresses, the stakes escalate, with Moriarty's plans growing increasingly ambitious and Holmes closing in on his true identity. The series balances its episodic structure with an overarching narrative, culminating in a confrontation that challenges the moral boundaries of justice and revenge. Themes of class struggle, morality, and the nature of heroism are woven throughout, offering a nuanced exploration of its characters and their motivations. The anime concludes with a resolution that leaves room for interpretation, reflecting the complexity of its central conflict.