OK, I give up -- I'm not familiar with the works of Wilkie Collins ... and I haven't been able to find any reference to a Collins story by this title. If anyone knows the Collins story on which this episode was based, please post the title of the original story.

A page at IMDB claims that this episode, "Shadows from the Grave", is an adaptation of Collins' story titled "Brother Griffith's Story of Mad Monkton". That can't be right? "Mad Monkton" is a very different story. The RMT adaptation of "Mad Monkton" (which also starred Kristoffer Tabori) aired on May 1 1975. 