The Beachcomber(1954)

Mr. Gray is the new Resident in Charge of the Welcome Islands in the Indian Ocean. The Islands are full of life, but the only other Europeans are the "sanctimonious, psalm-singing" brother-sister missionary team of Martha and Owen Jordans, and the Honourable Ted - a hard-drinking, womanizing social outcast whose English family pays him to stay away. Martha and Ted become an unlikely team when cholera threatens the islands and they must do their best to stop its spread.