A Reserve Bride (1966)

Synopsis by theflixtor - Lee Kei-hau is happily married with a son. His wife Wong Tai-chu, who has been complaining of discomfort lately, goes to see a doctor where her friend Wong Mau works as an assistant. Wong mixes up her report with that of a cancer patient. Believing her days are numbered, Tai-chu discusses with her mother to choose a second wife for Lee and finds the nurse So Lin-yung, Mau's girlfriend. Mau feels obligated to adhere to her request to hire So as family nurse. Lee urges his wife to make regular exercise a habit to improve her health but when his advice falls on deaf ears, he spurs her to action by dating the nurse. Infuriated by his wife's unexpected exhilaration, Lee accuses her of having an affair with Mau. Tai-chu retaliates by displaying great affection towards a man, her girlfriend Judy in disguise. Lee chases after the beau relentlessly and is told the truth by Judy. Mau's blunder is patched up with a smile, for his lover So, and for the reconciled couple Tai-chu and Lee.