When Sandra Marshall (Stanwyck) arrives in Mark Cadwell's estate and claims that she is his recently deceased nephew's widow, he is not very pleased and seems to be hiding something. Perhaps something about the circumstances of her husband's death? Her young sister-in-law on the other hand takes an instant liking to the new arrival whom she sees as friend who might release her from her uncle's oppressive rule.
In theory the above would be a good starting point for any film noir. True, this is not the most imaginative of settings: the stranger who arrives in a house full of secrets is hardly new. And yet the film fails abysmally. While Stanwyck does her best and is convincing as the newcomer exploring the household's secrets, there are three main factors on why the film doesn't hold.
First in the list must be Peter Godfrey, the director. Based on his IMDb credits, I imagine he would be nearly forgotten if it weren't for three films he did with Barbara Stanwyck: "Christmas in Connecticut" in 1945 and "Cry Wolf" and "The Two Mrs Carrolls" in 1947. The last is by far the best, and while I know "Christmas in Connecticut" is a personal favourite of many, it didn't do it for me at all. He seems to have been one of those directors who populated the studio system, doing what they were told to do without any imagination. He simply picks the script and does it by numbers. For a thriller the tension never amounts to much (unlike in "The Two Mrs Carrolls") despite a few attempts in that direction.
The second problem is casting. There are two obvious casting errors. One is Geraldine Brooks who plays the young sister-in-law. She was obviously been groomed by WB for stardom but someone along the way forgot to notice that the girl couldn't act. She is irritating, but in her defence her part is a bit thankless. Then there is Errol Flynn. At this stage you may want to stop reading, as I will discuss some of the plot. His casting is a clear attempt to play him against type. He was getting older, the drinking was clearly leaving traces on his face, and he wanted to prove himself as an actor. Two years later he would do the same in "That Forsyte Woman" (which I haven't seen yet). All that is fine, but it doesn't work; and for two reasons. Flynn's charm on screen depended massively on his ability of not taking himself too serious. But in 1943 he was accused of rape and suddenly saw his life turned upside down. Sadly, despite being cleared, his life and career were never the same again, in particular that infectious presence was gone and with it the ability of engaging with the audience. His range was not very wide and his confidence was probably low and the mix of all this produces a hybrid performance of menacing and dull insecurity. Five years earlier I suspect he would have been menacing because of his spider-like charm. He might have been a deadly villain, had he been allowed him to play one. More important than that, Flynn's casting is an issue because it either highlighted or caused the most serious problem with the film - the script.
Up to this film Flynn had been always the hero. Yet here there is a clear attempt to darken his image and I suspect that someone at WB got cold feet with this. Starting as Stanwyck's antagonist and the film's villain, a twist in the script says otherwise and suddenly there is a forced happy ending with the leading lady. Where Bogart was allowed to go dark, Flynn wasn't. And maybe a better actor would have pulled it off, but as the film stands it's just a curious failure with a good Stanwyck performance.