In Succubus, an ancient and powerful demoness, Lilith, returns to the modern world, possessing a young woman, Maya. Her presence brings terror as she seduces and kills her way through a small, unsuspecting town. Father Marcus, a priest with a dark past, teams up with Dr. Malcolm Weiss, a psychiatrist, to unravel the mystery behind Lilith's return. As Maya's condition worsens, the town spirals into chaos, leading to a final confrontation where ancient secrets and hidden sins are revealed. Only by embracing their inner demons can they hope to defeat Lilith