It is 1909. On the day that Princess Juliana was born, the psychiatrist Jan Giltay returned from a study trip to Vienna where he had become acquainted with the theories of Freud. In a clinic for the mentally imbalanced he becomes intrigued by Patient number 4. This one claims to be Alexander, the crown prince and youngest son of Queen Sophie and King Willem III who had been spirited away. At first Giltay had his doubts, but during the sessions of hypnosis it turns out that the patient knows a lot about the royal court. This thriller-like 8-part TV series has two narrative lines. As well as the story of the psychiatrist Giltay, the stories of Patient no. 4 is portrayed in flashbacks. These factual scenes show the history of the Dutch royal family between 1838 and 1884.