Stanwyck is really impressive in the film. Her athleticism stands her in good stead as she rides horses, journeys through the house in a dumbwaiter, drops from ceilings, and climbs fences in search of the truth (TCM calls her a midlife Nancy Drew!). She also has a magnificent wardrobe, designed by her favorite costumer, Edith Head. (Ms. Stanwyck ALWAYS looked amazing in riding clothes! Take a look at her 20 years later in The Big Valley!) But, while we are told Sandra is a PhD student in geology, that point is never pursued. She could be anyone, not a highly intelligent graduate student. We wished that her training had been actually used to solve the mystery.
As to Errol Flynn, if you are expecting him to be a romantic swashbucker, think again. His Mark Caldwell is a stiff, unattractive liar. And Flynn is not afraid to play him as such; it has been said that he ultimately relished the role BECAUSE it was so different from his usual fare, finally giving him a chance to play a more dramatic part. That the film attempts to tack on a romantic ending is a betrayal of the work of both actors. It's clear that Mark is genuinely suspicious of Sandra from the outset, and she doesn't like or trust him one little bit. He's also quite the male chauvinist: “Next time you hear some odd noise in the night, just follow the memorable custom of your sex and stick your head under the bedclothes." Why an educated woman would want him is beyond our ken. As a result, the ending of the film seems like it belonged to a different movie.
Quite frankly, a lot of the film doesn't make sense. Mark claims to be protecting Jim and sister Julie (Geraldine Brooks, in her first film role) from [spoiler] the family's hereditary strain of insanity, but he does little to actually CARE for them. He just keeps them hidden. And, when Sandra arrives, claiming to be Jim's bride (regardless of her claim to a marriage of convenience), Mark makes no inquiries to determine if Sandra might also be bringing an heir to the Demarest fortune within her. One would think he would confide in her, regardless of his fears that the family skeleton could have an impact on the political career of his brother.
Much of the suspense focuses on just WHAT is going on in Mark's laboratory. He is not called Doctor, so he isn't a physician (heck, his lack of knowledge about mental illness proves that). So, WHAT is he doing? We never find out (and when we see the lab, it doesn't look like anything was ever DONE in it. It's too clean to even be Mark's library!) The lab is more of a MacGuffin - just stuck in because working in a lab sounds mysterious and Frankenstein-y. Visions of Mark trying to reanimate Jim's dead corpse run through one's mind.
Errol Flynn was not the first person considered for the role of Mark - Dennis Morgan was the original thought (which would have been a reunion for him and for Stanwyck). And Dorothy Malone was to be Julie. Unlike Ms. Brooks, Malone would have come to the production with some film credits under her belt - including her standout performance as the bookstore clerk in The Big Sleep. But Brooks does a good job with a fairly thankless character. That same year, she would graduate to a better part as Joan Crawford's stepdaughter in Possession. Ultimately, Ms. Brooks would make her name in television, as a featured guest star in such shows as Dr. Kildare, The Fugitive, and Bonanza (where she appeared as Ben Cartwright's first wife - and Adam's mother - Elizabeth Stoddard Cartwright), and in the theatre. She died in 1977, aged 51 of a heart attack.
Totally wasted is Jerome Cowan as Mark's brother, Senator Charles Caldwell. We enjoy seeing Cowan, and one wonders why he was even bothered with this virtual cameo.
The music by Franz Waxman is quite excellent, and the costuming by Edith Head is exceptional. Her designs are classic, and could easily be worn today. Head was Stanwyck's favorite designer - according to Criterion, "Stanwyck was so enamored of the clothes that Head created for her characters that she hired her to design her personal wardrobe." According to Edith Head: The Fifty-Year Career of Hollywood's Greatest Costume Designer, Stanwyck was so impressed with Head's designs when they worked together in Remember the Night, that she asked for Head to be her costumer in all her films. Stanwyck had a notoriously long waist, which Head was able to camouflage, changing the direction of Stanwyck's film career to include more "dress roles".
So, while Cry Wolf starts well, by the end it feels rushed and is not really all that convincing. The New York Times was also not a fan of the film. As this TCM article points out, critical opinion in general was not very kind. However, you do have an opportunity to see Errol Flynn in a role that was very unconventional for him (and hints at the character of Soames in That Forsythe Woman), Stanwyck looking stylish, and a young actress at the start of her career. Here's a trailer to the film: