Dylan Dog is a private investigator specializing in supernatural cases in New Orleans. Retired from his former life as a mediator between the human world and the undead, he is drawn back into action when he receives a call from a distraught client, Elizabeth, whose father has been mysteriously murdered. Upon investigation with his quirky, zombie assistant Marcus, Dylan discovers that the city's concealed underworld of vampires, werewolves, and zombies is on the brink of a full-blown war. Among these creatures, a powerful artifact known as the Heart of Belial comes into play, believed to grant immeasurable strength and darkness to its possessor.

Dylan uncovers that the artifact's recovery is key to both the escalating turf wars and Elizabeth's father's death. As he delves deeper, Dylan is forced to confront various formidable supernatural beings, each with their own stake in the chaos. He encounters Gabriel, a cunning vampire leader, and Vargas, a violent werewolf alpha, both vying for control over the artifact. His pursuit of the truth leads to battles and alliances he never expected. As the city's balance teeters on the edge, Dylan must navigate this perilous world, using his wit and courage to prevent an impending disaster, all the while coming to terms with his own haunted past.