There's Always Tomorrow (1956)

Toy manufacturer Clifford Groves is married to Marion, with three kids, but lately life has become drab and routine. A former co-worker, Norma Miller Vale, turns up unexpectedly and is now a glamorous fashion designer.

Marion has to pull out of a planned vacation but urges Cliff to go alone. There he runs into Norma, who is divorced and lonely. They ride horses together and dance. But they are spotted by Cliff's teenage son Vinnie, who has just arrived with his girlfriend Ann.

Vinnie confides in sister Ellen that their father might be having an affair. Norma is invited to dinner, but the evening turns awkward. Vinnie later overhears his dad arranging to meet with Norma. He and his sister appeal to Norma not to break up their parents' marriage.

Cliff is indeed in love with Norma now and tells her so. She feels the same, but feels she must leave. At home, Cliff looks longingly out a window as a plane flies overhead. He and Marion are left to contemplate what is to become of them.