I find
The Witch of the Low Tide a bit funny, because it is very obviously structured in a way to make the synopsis more exciting, but misleading.
The "intended" synopsis is: Psychiatrist David Garth is infatuated with the young widow Betty Calder. However, one night a Scotland Yard inspector appears before Garth and informs him that Betty is, in fact, a blackmailing Satanist prostitute. That night, one of Garth's friends identifies Betty as the woman who tried to strangle her aunt and then disappeared from a locked basement. And the next day, a corpse turns up in the bathing pavilion of Betty's house, even though there were no footprints in the surrounding sand. The Scotland Yard inspector insists that Betty is behind these crimes. Will Garth be able to discover the truth of these crimes and, more importantly, the truth of Betty herself?
The actual plot: All of the above, except we quickly learn that Betty has an older sister who looks just like her, Glynis Stukeley. Glynis is the blackmailing Satanist prostitute, Glynis is the person Garth's friend actually claims she witnessed, and—Glynis is the corpse in the bathing pavilion, so we can't pin that one on her. But two out of three ain't bad!