"Kaitō Lupin - 813 no Nazo" is a 1979 anime series based on Maurice Leblanc's Arsène Lupin stories, specifically adapting the novel "813." The narrative centers on the enigmatic gentleman thief Arsène Lupin, who becomes embroiled in a complex web of intrigue, murder, and political conspiracy. The story begins with Lupin being framed for the murder of the wealthy businessman Kesselbach. To clear his name and uncover the truth, Lupin must navigate a labyrinth of clues tied to the mysterious "813" code, which holds the key to a larger conspiracy involving European royalty and powerful figures.

The plot unfolds as Lupin encounters a diverse cast of characters, including his loyal ally and rival, Inspector Ganimard, who is determined to capture him. Lupin's quest leads him to cross paths with the cunning and resourceful Sonia Krichnoff, a woman with her own hidden agenda tied to the "813" mystery. As Lupin delves deeper, he uncovers a plot orchestrated by the sinister criminal mastermind known as "The Emperor," who seeks to manipulate political events across Europe. The stakes escalate as Lupin races against time to prevent a catastrophic assassination and expose the true culprits behind the conspiracy.

Throughout the series, Lupin's intellect, charm, and resourcefulness are on full display as he outwits adversaries, deciphers cryptic clues, and navigates dangerous situations. The narrative is driven by a blend of mystery, action, and suspense, with Lupin's moral ambiguity adding depth to his character. The series maintains a focus on the intricate plot, with each episode building toward the resolution of the central mystery. The interplay between Lupin and his adversaries, as well as his complex relationships with allies and enemies, adds layers to the story, making it a compelling adaptation of Leblanc's classic tale.