Like many film stars of the time, Joan Crawford did quite a bit of television in the 50's and 60's. Many people are familiar with her appearances on The Virginian and Here's Lucy, as well as her failed pilot, Royal Bay, which became the feature Della but before that she starred in one-off episodes of quite a few anthology series. In this one - Zane Gray Theater - she plays twins in a twisted story of family relationships gona awry.
This series has yet to be available on DVD, though you can get unofficial collections on various sites. This episode has been uploaded to YouTube by shanecincy. Part one is above.
Obscurity factor: 10 (hard to find, almost completely forgotten.