Val Lewton did not like the article "I Walked With A Zombie" by Inez Wallace that had been optioned so he adapted the story to fit the novel "Jane Eyre" because he felt the article's plot was too clichéd.
Edith Barrett, who played the mother, was only 3 years older than James Ellison, who played her younger son, Wesley. She actually was 2 years younger than Tom Conway, who played her older son, Paul.
In the script, the fictitious island is very explicitly identified as being owned by the United States. None of these items (such as a prominent American flag flying at the harbor) made it into the film, and items like the Island's association with British Columbia (where Betsy is from) suggest that it might instead be a current or former British colony.
The two figures seen walking along the beach during the opening credits are Frances Dee and Darby Jones.