Adapted from a Saturday Evening Post serial by Frank and Marian Cockrell, Dark Waters stars Merle Oberon as heiress Leslie Calvin, a woman with a neurotic aversion to water. This stems from the fact that in her childhood, Leslie was one of four survivors of a torpedoed steamship. Preying upon Leslie's fears, conniving Mr. Sydney (Thomas Mitchell), a guest at the Calvin family's Louisiana plantation, concocts a campaign of terror designed to drive the poor girl crazy so that he can claim her vast inheritance. Sydney and his cohorts also have the presence of mind to murder all of Leslie's closest relatives, leaving her utterly helpless.