This movie is a whodunit dressed-up like a mix of Midnight Faces (1926) with The Cat and the Canary (1927).
There is a clever twist to how the murder itself is effected, but unfortunately the story containing it is rather meager; it could have been presented in perhaps 20 minutes, rather than in the hour expended.
As in various other films, an independent investigator whose behavior is plainly illegal is tolerated rather than taken into custody or even expelled. The explanatory device, in this case, is that the officer in charge is in love with her, but credibility is over-stretched.
That officer ultimately solves the case using evidence withheld from the audience while in his possession; that evidence is not particularly surprising, but it also is not sufficiently strong, especially given that the officer had to rely upon testimony as to events at the time of the murder, rather that being himself a witness to it.
Another flaw in this story, common to a great many films of the period, is the presence of a stereotyped black servant -- dim-witted, superstitious, cowardly, and slow-moving except when terrified.