There's Always Tomorrow is a remake of a 1934 film of the same name. Fred MacMurray is a toy company executive whose wife (Joan Bennett) and kids (Gigi Perreau, William Reynolds and Judy Nugent) take him for granted. Barbara Stanwyck is Fred's former girlfriend, whose own business activities result in a surprise reunion.
MacMurray falls back in love with Stanwyck and prepares to leave his family. MacMurray's children go to Stanwyck and politely ask her to back off. She does so, and MacMurray's wife Bennett, who's been out of town during all this, is none the wiser.
In the original There's Always Tomorrow, the male and female leads (Frank Morgan and Binnie Barnes) were farther apart age-wise, making their brief encounter all the more poignant.