Inspector Holtz was a police official in Visaria who was close friends with Dr. Franz Edelmann. When an unruly Larry Talbot arrived, demanding he be locked up or else he'd turn into a werewolf and kill someone, Holtz obliged him and summoned Edelmann. Edelmann arrived with his associate Miliza Morelle, and the three of them witnessed Talbot's transformation into a hideous werewolf. At Edelmann's behest, Holtz kept Talbot locked up all night. Come the dawn, Talbot returned to human form, and Holtz gave the emotionally troubled lycanthrope over to the Doctor's care at the Niemann estate which Edelmann had taken for his own following Niemann's death.
Later, when Edelmann became infected with the blood of Dracula, turning him into a monster, he attacked and killed his groundskeeper Siegfried. An angry mob, led by Holtz and his men, pursued the murderer, who they didn't realize was Edelmann, back to the Niemann house. Holtz suspected Larry Talbot of having committed the murder, due to having witnessed his transformation into a werewolf, but Edelmann, after returning to normal, assured the Inspector that this was impossible because he'd cured Talbot of his lycanthropy.
Despite the protests of Siegfried's grieving brother Steinmuhl, Holtz took Edelmann at his word and took his search elsewhere. After days passed and with no sign of the killer being caught, tensions began rising in Visaria. Steinmuhl found evidence that Eldemann had killed his brother, but Holtz was skeptical and warned Steinmuhl against inciting mob violence against the scientist.
Nevertheless, he and some of his men took it upon themselves to head to the Niemann house and confront Edelmann about the evidence. They arrived just as Edelmann, transformed once more, was reviving Frankenstein's Monster. Holtz and one of his men entered Edelmann's laboratory where the Monster attacked them. He knocked the other officer out, and threw Holtz against some of the electrical equipment, where the Inspector was violently electrocuted and killed.