Hayley Mills admitted to being utterly besotted with her handsome male co-star Horst Buchholz, even though he was always putting her off her lines by goofing around behind the camera.
Hayley Mills' film debut at the age of 12.
Horst Buchholz's English-speaking debut.
The role for Gillie was originally written for a boy. When J. Lee Thompson went to see John Mills, he noticed that tomboy Hayley Mills had her hair like a boy, and he offered her the part.
The scene in which Gillie is telling the police about the murder was ad-libbed by Hayley Mills. John Mills and J. Lee Thompson told her the basic plot for the scene and told her to make it up.