The April Fools (1969)

Virtually the first third of 'The April Fools' takes place at a trendy party held by sharkish executive Ted Gunther (Peter Lawford). It is here that Howard Brubaker (Jack Lemmon), one of Gunther's employees, makes the acquaintance of the boss' lovely young trophy wife Catherine (Catherine Deneuve). It happens that Brubaker is unhappily wed to Phyllis (Sally Kellerman, who gives an excellent performance in an essentially one-note role) and that Catherine is equally unhappy in her relationship with Gunther. The two lost souls run off together, planning to fly to Paris...