Thriller S02 E05 Ring Once for Death

"The Spine-Chilling 70s Anthology"

A con man posing as a butler, with the help of his girlfriend posing as a maid and a disreputable doctor, poisons his employer, a wealthy widow. Michael Jayston, Nyree Dawn Porter, Barry Nelson, Thorley Walters, Janet Key, Victor Winding, Clare Sutcliffe, Richard Oldfield