Star Richard Widmark and original director Robert Totten had "artistic differences," and Totten was replaced by Don Siegel. When the film was completed, Siegel, saying that Totten directed more of the film than he did, refused to take screen credit for it, but Widmark didn't want Totten's name on it. A compromise was reached whereby the film was credited to the fictitious "Alan Smithee" (originally to be called Al Smith, but the DGA said there had already been a director by that name), thereby setting a precedent for directors who, for one reason or another, did not want their name on a film they made.
Don Siegel took over from Robert Totten after a 25 day shoot, and completed it in a further 9 days.
The Richard Widmark character is in a relationship with the Lena Horne character: in other words, an interracial relationship. That aspect of things is not a plot point in the movie - she's his girlfriend, and nothing more is said. At the time of the movie's release, this was touted by some involved (Widmark for one) as a sign that society had finally reached the point where such things were no longer a controversy or a big deal, and didn't need to be dealt with as part of the narrative.
Don Siegel says in his biography that Richard Widmark did not like playing in a movie directed by Robert Totten.