The film script was written by Derek & Donald Ford. Henry Craig was an uncredited contributor. The story was written for the 1965 film shown here :
https://www.youtube.com/watch?v=ey5m...l=EliseoSantos
The trailer to the film :
https://www.youtube.com/watch?v=1w8i...nboundPictures

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In 1966, the film was made into a novel by Ellery Queen and Paul W. Fairman. The novelisation is unusual in that it adds a framing story wherein Ellery Queen reads a manuscript that re-tells the actions of the film. The framing story was written by Ellery Queen and the novelisation of the film itself by Fairman.
A film preceding a novel is unusual.

https://www.goodreads.com/en/book/show/2805586
https://www.youtube.com/watch?v=ey5m...l=EliseoSantos
The trailer to the film :
https://www.youtube.com/watch?v=1w8i...nboundPictures

*********************************************
In 1966, the film was made into a novel by Ellery Queen and Paul W. Fairman. The novelisation is unusual in that it adds a framing story wherein Ellery Queen reads a manuscript that re-tells the actions of the film. The framing story was written by Ellery Queen and the novelisation of the film itself by Fairman.
A film preceding a novel is unusual.

https://www.goodreads.com/en/book/show/2805586