This is one of the first films where the beating human heart is portrayed during open-heart surgery.
Olivia de Havilland and Robert Mitchum prepared for their roles by attending eight operations. Broderick Crawford attended an autopsy for his autopsy scene and promptly got sick.
There was a such a boisterous atmosphere on this shoot that Robert Mitchum described it as "not so much a cast as a brewery !"
Robert Mitchum (Lucas Marsh) and Gloria Grahame (Harriet Lang) were once related by marriage as his brother John Mitchum was formerly married to her sister Joy Hallward.