Wij Alexander is based on the story of the third son of King Willem III and Sophie van Württemberg. According to the history books, Alexander only had a short life; 1851 to 1884. Jan Giltay, psychiatry student, is really amazed when he gets acquainted with a certain patient no.4 in a clinic, who claims to be Prince Alexander. The man indeed seems to know a lot about the royal family and a life at the court. Not only his story indicates he's a royal, but clues from the outside seem to indicate he could be the 'forgotten' crown prince. Moreover patient no.4 would be in the possession of a secret chest with information which could lead to the downfall of the royal family.
Patient no.4 is taking care of the wounded Jan. Both of them are now wanted by the French police. Catharine, together with De Vreeze, look for Jan in Paris. And of course everyone is still looking for the secret chest.