I hate reading reviews that say something like, 'Don't waste your time, this film stinks on ice.' It does to that reviewer yet for me, it may have some sort of naïve charm. If you like the other 'Whistler' series films, this one will be watchable. If you like 40s noirish films, this one will be watchable.
This film is not as good, in my opinion, as any of the earlier series entries which starred Richard Dix as the protagonist. It's much slower, and the plot is trite. You've seen this same narrative device used in many other films, and usually better.
But the acting is good, and so is the lighting, and the dialog. It's just lacking in energy and you'll likely figure out exactly what's going on and how it's all going to come out in the end not more than a quarter of the way through.
The 'Whistler' series is semi-noir, and there character, mood, lighting, camera movement and angles are more important than the story itself. But this film is not noir. It's too light weight and Hollywood innocent for that. Neither Richard Dix's character nor those of any of his ladies in the previous films had to come to a good end. You just never knew until the end.
But still, I'll recommend this one for at least a single viewing. I've watched it at least twice myself, and got a reasonable amount of enjoyment out of it both times.