A doctor who cannot figure out what is wrong with his patient refers him to a detective, whom he hopes will be able to discern the cause of his mysterious illness.

Max Landa
as Detective Landa

Reinhold Schünzel
as Freiherr von Mohrungen

Conrad Veidt
as Wilmos, sanatorium director

Hilde Woerner
as Siegnis, maid

Marga von Kierska
as Frau von Riberac