In early 20th-century Austria, brilliant but self-destructive expressionist poet Georg Trakl shares a fierce, drug-fueled, and deeply forbidden incestuous passion with his younger sister, Grete. As the crushing weight of societal judgment forces Grete into a marriage of convenience with an older professor, the siblings continue their secret, volatile physical affair, driving them both down a dark path of psychological torment, addiction, and ultimate madness.