Carroll Baker was concerned about being typecast after her provocative role in the controversial Baby Doll, and began refusing parts. The studio offered her a choice of roles and she chose this one because it was as different as possible.
The last movie shot at the Warner Brothers Ranch in Calabasas.
Warner Bros. originally intended this property as a Technicolor vehicle for Bette Davis, who made a Technicolor screen test as the young nun. The project was soon canceled, and years later, when asked about it, Ms. Davis quipped, "Of course, the only thing I've never played is a nun!"
Warner Brothers had planned to make a film version of "The Miracle" as early as 1942, with Henry Blanke producing. The 1942 version was supposed to have followed the original play more closely, but the project was scrapped. It was revived in 1952, but was again scrapped, and in 1959, Warners finally released a film of it. The story was heavily revised, and the time period changed from the Middle Ages to 1810.