"Hanussen" tells the story of a man whose life parallels Hitler's rise to power. Austrian Klaus Schneider, a World War I veteran, is wounded and cared for by Dr. Emil Bettleheim. Bettleheim discovers Schneider's unique abilities of empathy and clairvoyance, which he uses to help suicidal patients.
After the war, Schneider changes his name to Eric Jan Hanussen and moves to Berlin with his manager and lover. There, he becomes a renowned hypnotist and clairvoyant, performing in halls and theaters. Hanussen always speaks the truth, catching the attention of powerful Nazis.
He predicts the Nazis' rise to power, which serves as good propaganda for them, but also foresees their violent actions, which is not well-received. Hanussen finds himself in pain and at risk, leaving his future uncertain.