CACTUS FLOWER is the story of a dentist (Walter Matthau) who has told his young girlfriend that he's already married so she won't get any ideas about marriage. The girlfriend decides she must meet the wife--panicked, the dentist asks his dowdy assistant (Ingrid Bergman) to pose as his wife. When the meeting is arranged, he finds that his assistant has blossomed into a beautiful woman. Much to his own surprise, the dentist begins to pursue--his own "wife."