Der Verloreue (The Lost One) was the only directorial effort by actor Peter Lorre. In keeping with Lorre's established screen persona, this is a tale of stark terror, disillusionment and defeatism. The actor stars as Dr. Rothe, a German research scientist who during WW2 discovers that his fiancee has been selling his scientific secrets to the British. In a fit of pique, he murders her, but is not punished for the crime, which is passed off by the Nazi authorities as justifiable homicide. Unable to console himself to his sweetheart's betrayal, Rothe wanders the countryside, killing every woman who reminds him of his lost love - while the Gestapo dutifully continues covering his tracks, even declaring him legally dead so that he can escape imprisonment. In a plot twist worthy of Fritz Lang, Lorre puts himself on trial and metes out his own punishment. Not entirely successful, Der Verloreue is still a fascinating exercise in fatalism from one of the cinema's most distinctive talents.
~ Hal Erickson, All Movie Guide