Heinrich "Heinz" Schneider, a German immigrant doctor of physics with no family, dedicated himself to scientific study. He served as the principal scientist for Project LEVIATHAN, researching supernatural abilities derived from "Witch DNA." Assigned to care for and study Ellis, a young girl artificially engineered with such DNA within an isolated remote laboratory, Schneider initially remained detached, strictly focused on his research objectives.

His relationship with Ellis evolved significantly over time. Despite initial difficulties in eliciting her powers, Schneider developed genuine care for her well-being. This shift coincided with increasing ethical concerns regarding Project LEVIATHAN's methods, particularly the harsh tactics employed by director Douglas Rosenberg to force Ellis' powers to manifest. Schneider's growing unease with Rosenberg's actions prompted him to question the project's motives.

Supervised outings, including fishing trips permitted by Rosenberg as part of behavioral conditioning, deepened their bond, fostering mutual affection. Ellis developed feelings for Schneider. Resolving to protect Ellis, Schneider planned to abandon the project. During a private Thanksgiving dinner celebrating their planned escape, Rosenberg intervened. Schneider was fatally shot by Rosenberg during the confrontation. With his final act, Schneider urged Ellis to flee, sacrificing himself for her safety.

Ellis became the prime suspect in Schneider's murder, though her memories of the event were fragmented by trauma and possible conditioning. This accusation set Ellis on a fugitive path, driving her quest for answers about her past and Schneider's death. Schneider's role as a compassionate guardian and victim of Rosenberg's machinations established his lasting influence on Ellis' journey. Flashbacks throughout the series depicted his kindness and their meaningful connection, his death remaining a pivotal element in Ellis' quest for truth and self-discovery.