Now, for the big problem, which is that we do not know what the main theme of the movie is. You see, the story has a black man (the murder target) playing the part of the white man's brother. No one in the movie sees this, and they act as if the color and also the huge physical differences aren't there. We in the audience know. This distraction causes us to wonder what's going on for a good hour. What's the point? It seems to be that we are not color-blind and not appearance-blind. Yes, we do distinguish people by their looks. Actors have to be made up to play parts.
Maybe the point is to make us remember the movie. The movie comes across as a low-budget experimental effort, and as a shaggy dog story (long, inconsequential, absurdly pointless) but in a noir vein. The best part of it is Dennis Haysbert and his character, as he decides to adopt a new identity.
The Freudian shrink seems to be made intentionally stupid and devoted to dream analysis but incompetent at it. At the end, he intones that Haysbert, who now recalls who he really is, is going wrong by becoming his brother; and there will be blowback. For example, he might be found guilty of killing his father; but the story stops with Haysbert, who was poor, enjoying not only his new-found wealth but the love of his white female doctor. He seems also to be the target of Dina Merrill's frustrated love. That's why dragging out the amnesia and shutting off an act 3 bothers me.
Critics seem to think that the black/white gimmick didn't work. My opinion is that since the movie is played for real and not surreal, it's silly to have everyone in the movie looking at this big black guy and "seeing" a scrawny white guy. We know that the actors have to act this way, because that's the story. We are then looking at how well or badly they are doing this with a straight face. Are they succeeding at this illusory task? Finally we give up and accept the unreality ourselves, sort of provisionally or for the duration of the movie, at which point we are left with the story itself.