André Boyer, widely known by his underworld alias Baron Spider, is the primary antagonist of the series. On the surface, he leads a life of immense respect and privilege as a university professor, leveraging his handsome appearance and sharp intellect to navigate the highest circles of society, including the political world and financial sectors. This public persona is, however, a complete fabrication, as he is also the merciless kingpin who secretly controls a powerful criminal organization operating in the shadows.

Boyer’s motivations are rooted in a deep-seated greed for power and control, which he maintains through a facade of charm and legitimacy. He is directly responsible for the financial ruin of Inspector Fabre’s parents through deceit, which establishes the central conflict of the series and makes him the target of the detective’s personal vendetta. In his role as the story's main villain, Boyer serves as the ultimate obstacle for Inspector Fabre, representing the height of corruption and criminal mastery that the hero must strive to expose and dismantle.

His key relationships are defined by manipulation and opposition. He is the sworn enemy of Inspector Fabre, who is constantly monitoring his activities while investigating other crimes. Boyer also secures an engagement to Charlotte, the daughter of a lodging house owner, by deceiving her honest parents, though she eventually discovers his true nature and flees to become Fabre’s assistant. Throughout the narrative, Boyer shows no meaningful development or change of heart, remaining a consistently formidable and duplicitous figure whose primary goal is to protect his double life and expand his illicit empire. His notable abilities lie not in physical prowess but in his high intelligence, social cunning, and the vast resources at his command as a crime lord.