Nightmare Castle

Here is a nice little horror movie starring ever-beautiful actresses Barbara Steele.
A Victorian scientist returns early from a medical convention to find his wife and gardener having too friendly a time together at the greenhouse, so he promptly ties them up and tortures them to death. Pretty standard so far.
Right before he kills his wife she informs him that her money and estate will default to her crazy sister living at an asylum if she dies. He kills her anyway, and proceeds to marry his dead wife’s crazy sister.
Though, there is something odd about her sister Jenny, I mean besides being crazy and all.