Premise: The Key is a 1958 British war film set in 1941 during the Battle of the Atlantic. It was based on the 1951 novel "Stella" by Jan de Hartog (later republished as "The Distant Shore" and "The Key") and was directed by Sir Carol Reed. William Holden, Sophia Loren and Trevor Howard starred in the production.
Hypothesis: Sophia Loren was one of the most popular and beautiful actresses working at the time of the film.