The actual Art Deco apartment building used in the film (located at 1360 Montgomery St in San Francisco) is still standing as of December, 2008. The actual apartment is marked by a cardboard cut-out of Humphrey Bogart, which can be seen from the street. The site is visited frequently by fans of vintage film noir.
Humphrey Bogart's complete uncovered face is not seen clearly until 62 minutes into the movie, when his character finally removes his bandages and looks into a mirror. All previous scenes with the character are either shown from his point of view or have his face obscured with shadows or bandages.
Warner Brothers studio head Jack L. Warner was not pleased to discover that the face of one of his biggest stars, Humphrey Bogart, is not seen for the first half of the movie. But the time Warner knew this, the film was too far along to be changed.
Between the film's unorthodox "first person perspective" and Humphrey Bogart's negative press from his support of the Committee for the First Amendment established in the face of the hearings being done by the House Un-American Activities Committee led to the film having a poor performance at the box office.
The playing on the phonograph of "I Guess I'll Have to Change My Plan" as Vincent is recuperating at Irene's apartment after his surgery may have been an arcane wink to the audience. It was used in the previous Humphrey Bogart and Lauren Bacall movie The Big Sleep (1946), when Vivian Rutledge (Bacall) paid off Marlowe (Bogart) at the gambling joint-nightclub.
When Vincent Parry looks at Irene Jansen's scrapbook he sees a newspaper clipping about her father dying in prison, having been convicted of killing his wife, Irene's mother. The photo in the clipping is of Delmer Daves, the director of the film.