So often in film noir one finds themes of the lone man (or lone individual) who faces a very dirty, tricky, dark world and makes his way through that world to discover the truth about something. Often that truth is a hidden act such as a crime, often involving murder. The protagonist (or detective) goes through all the tricks of the evil person or persons in the story, is sabotaged or fooled, faces many deceptions and dangers. Often this involves self-sacrificial behavior on the part of the hard-boiled detective. He has a code, after all, even if he's the only one left in the world who follows that code.
Jesus tells His disciples, "Indeed the hour is coming, yes, has now come, that you will be scattered, each to his own, and will leave Me alone. And yet I am not alone, because the Father is with Me" (John 16:32). He'll be the one to walk the straight path, the true path, the one of duty and courage, even when the rest are scattered. He will pay the price. He'll be deserted by friends and disciples, but not by His code nor His Father in heaven, the One whom He serves. He's loyal to the end, and has the courage and integrity to be that person even if he has to do it alone, on His own. Even when friends desert Him. This is the startling light in the darkness, the existential reality of the divine who has come into the world as one of us, and faces the grim "facts" of this world on our behalf, to transfigure what looks true but is just an illusion, to expose the lies of death and evil.
