In a remote part of Florida, Coral Platt, a sinister woman has married a man considerably older than she. For reasons sufficient to her, she wants him out of the way and plans an ingenious though slow murder by poison. She has succeeded in making it seem that Marvin is dying through natural causes. However, she is forced unexpectedly to play hostess to two women who have come to Florida. The women stay longer than they planned because they have begun to suspect what Coral is up to.