Dame Elizabeth Taylor personally called Bette Davis to offer her the role of Mrs. Helen Fiedke. Davis was interested, but eventually turned it down after Taylor told her that they were shooting the movie without a complete script.
Muriel Spark described her novella, a favorite of hers, as a "whydunnit," because the plot, more metaphysical than realistic, is not about what events that happen, but why they happen. The answer is left to the reader to decipher.
Paramount Pictures first announced this in 1970, with Herbert Ross directing from a Frederic Raphael script.