Honestly, Eleanor Parker brought the film down for me
And when I say this I mean nothing whatsoever against her personally(I mean, how could I? It's not like we have morning tea together or anything), but her acting- at least as far as this film is concerned- has a quality about it that I have never particularly enjoyed in any of my viewings of the film; it's the one thing that really bugs me about Detective Story, as a matter of fact. I can't really put my finger on what is so wrong but many of her line readings are so hokey and artificial that I honestly cannot help but cringe when the film calls for her to do some real drama. For me, at least, Parker gives the impression that she is reveling in the way she reads the words rather than employing them to portray a character- that she's doing more "line-reading" than "acting".
That's not to say that the the rest of the performances are particularly naturalistic- it's a play-based melodrama from the early 50s, after all-, but where the mugging and scene-chewing of Lee Grant and Joseph Wiseman feel appropriate to and furthers those characters, in Parker's case I think it just bogs her character down.
Of course, this is all my opinion. I hope I didn't ruffle any feathers, and I would be interested to hear opinions to the contrary.