Scarlet Street dropped in 1945, and its director is the estimable German-born director Fritz Lang. Lang is most remembered for his early German films like 'Metropolis' and 'M', but he had a long career, shooting his last film 'The Thousand Eyes of Dr. Mabuse' in 1960.

Both 'M' and 'Metropolis' deal with very dark themes. 1931's 'M', in fact, can be considered the template for the modern 'serial killer' film. Lang's film 'The Testament of Dr. Mabuse' was banned in Germany for its treatment of the rising Nazi regime. The charge against the film was 'incitement to public disorder', mostly because Lang put some of the Nazis' phrases into the dialog of Dr. Mabuse in a way the Reich found unflattering. By Lang's own account, he was informed of the film's banning from Joseph Goebbels directly. He further claims that despite the banning, Goebbels was impressed enough by his filmmaking to offer him the chance to run German studio UFA. He did not take the job, and he eventually fled Germany. He made his way to the United States in 1936.

In 1945 when 'Scarlet Street' was made, US films were governed by the Motion Picture Production Code (https://en.wikipedia.org/wiki/Motion_Picture_Production_Code), more commonly referred to as 'the Hays code'. This document set out strict and perversely arbitrary standards for what movies were allowed to show. The code included twenty-five subjects that required 'special care' to pass inspection:
  1. The use of the Flag;
  2. International Relations (avoid picturizing in an unfavorable light another country's religion, history, institutions, prominent people and citizenry);
  3. Arson;
  4. The use of firearms;
  5. Theft, robbery, safe-cracking, and dynamiting of trains, mines, buildings, et cetera (having in mind the effect which a too-detailed description of these may have upon the moron)
  6. Brutality and possible gruesomeness;
  7. Technique of committing murder by whatever method;
  8. Methods of smuggling;
  9. Third-degree methods;
  10. Actual hangings or electrocutions as legal punishment for crime;
  11. Sympathy for criminals;
  12. Attitude toward public characters and institutions;
  13. Sedition;
  14. Apparent cruelty to children and animals;
  15. Branding of people or animals;
  16. The sale of women, or of a woman selling her virtue;
  17. Rape or attempted rape;
  18. First-night scenes;
  19. Man and woman in bed together;
  20. Deliberate seduction of girls;
  21. The institution of marriage;
  22. Surgical operations;
  23. The use of drugs;
  24. Titles or scenes having to do with law enforcement or law-enforcing officers;
  25. Excessive or lustful kissing, particularly when one character or the other is a "heavy".
To a 21st-century film viewer, the idea of making an involving crime drama while tiptoeing around theft, robbery, safecracking, brutality and possible sympathy for criminals seems just about impossible. Like many directors of his era, however, Lang became rather expert at evading the censors while still smuggling in the subversive elements he thought his film required.

'Scarlet Street' is a good example of the tightrope walk that was filmmaking in the Hays era. The darkest elements of the story are not discussed head on, but are very visible to anyone with more sense than a a censor . The relationship between Johnny and Kitty is never clarified in dialog and leaves just the barest shred of plausible deniability. The nature of Christopher's marriage to Adele also has dark undertones not verbalized. There is a policeman who seems to admit to a great deal of misconduct and there's a vibrant trade in petty crime and vice kept mostly just offscreen. Most importantly, the film breaks a cardinal rule of the era - a known murderer is not brought to justice.

That's probably my favorite thing about 'Scarlet Street'. The result of the arbitrary Code restrictions is a movie that exists in two versions, shown simultaneously. Noir before noir, and a little meta before meta.