Heinrich "Heinz" Schneider, a German immigrant physicist, contributed to Project Leviathan—a U.S. government initiative to engineer artificial witches through molecular manipulation based on Maxwell's Demon theory. As primary caretaker and researcher for test subject Ellis during her childhood, he initially performed rigorous experiments to activate her latent abilities but gradually developed paternal affection for her. Disturbed by the project's unethical progression under Douglas Rosenberg, Schneider planned to escape with Ellis. On their intended departure night, during a celebration with Ellis, Rosenberg fatally shot him through a window. Ellis, nearby, was drenched in his blood and falsely blamed for his murder.

His death triggered Ellis’s amnesia and ignited her journey. Flashbacks reveal his consistent kindness toward her, depicting their bond’s evolution from scientific scrutiny to authentic care. Schneider’s legacy hinges on his discredited physics theory defying thermodynamics, which underpinned Project Leviathan. His murder remained an unsolved mystery until Rosenberg’s guilt emerged. In the series’ climax, his spirit manifested to Ellis after her resurrection, thanking her before vanishing. His scientific work and ethical struggle directly shaped Ellis’s powers and the project’s downfall.