Hypnotist and magician Dr. Vogler heads a group of travelling players, which includes his wife Manda (Ingrid Thulin) dressed as a male assistant. They are examined and humiliated by Dr. Vergerus (Gunnar Bjørnstrand), a cynical medical officer. During a performance convened for the medical officer and his committee, Vogler exerts his revenge. When the tables are turned again, the magician perpetrates an incredible illusion on the unbelieving doctor, but is now trapped within his own mystery...