While the film throws out a few red herrings at the beginning to make the viewer believe that this is a Gaslight-type thriller, for a Hitchcock film the mystery and suspense elements are quite subdued, making this more a historical drama than anything else. The plot is propelled not so much by the actions of malicious characters (although there is some of that) but also by the misunderstandings among the non-bad characters about each other's past and intentions. The movie frustrated me because these non-bad characters seemed to deliberately mislead other characters and the viewer for no other reason than to propel the plot along, so the ensuing tension feels artificial, as does the you-can't-run-from-the-past theme. This isn't helped by the forgettable performance of Michael Wilding, who frankly is a rather bland hero.
Under Capricorn is unusual for a Hitchcock film in that it explicitly takes on the role of class and examines how class distinctions can trap people and make them unhappy.
The setting was also very drab--the colors, especially in interiors, felt washed out. I don't know if this was the fault of the filmmaker, or aging, or that of the transfer ( I saw the Image DVD edition of this film). Because the plot is so boring, I don't think Hitchcock was able to flex his directorial talents very much. The only thing that really stands out is an impressive long take where the camera follows Wilding around Joseph Cotton's estate as he is introduced to the other guests.