The Diary of a Husband serves as an illustration for the arrival of the white-collar economy, in which the extended family is replaced by the smaller nuclear family. It is a story about four pals who work at the same office, which, like other white-collar workplaces, has become the men's primary site of life, where livings are made and friendships fostered. Meanwhile, their wives have fostered something of their own—a brigade to catch cheating husbands. Much comedy is then generated by the cat-and-mouse game between the men and the women...The battle line drawn here between the sexes remains for years, to the extent that this very same story has been retold many times in Hong Kong films, including Men Suddenly in Black, the 2003 Pang Ho-cheung film with a similar Chinese title.
In order to bring about the return of a prodigal son, Hoi Yau-lung asks his fiancee Fa Sau-lan to administer 'the beauty ruse' to trick his cousin Wan Kam-cheung into squandering all his money. When Wan is reduced to penury, he encounters his wife Suk-ching and learns from her the whole story. Wan realises his faults and resolves to turn over a new leaf.
Yuk Yin's father dies and her mother remarries to settle the debts. Yuk Yin lives with Auntie Wong. From then on, Chi Hung, Auntie Wong's son and Yuk Yin live and play together. But the Wongs move away. Yuk Yin stays with her mother. Her stepfather is mercenary. When Yuk Yin grows up, he pushes her to get married to get money. Considering her daughter's future, Yuk Yin's mother sends her away. Yuk Yin works in a restaurant. When she learns that her mother is ill, she marries a dying rich young man to get money for her mother's treatment. After her mother's death, Yuk Yin gets married immediately, but her husband dies on the wedding night. Her mother-in-law sees this as unauspicious and expels Yuk Yin. Later, Yuk Yin chances upon Chi Hung. They are still in love. They married and have a son Kwok Wah. But Chi Hung dies. Yuk Yin works as a dance girl to support their living. Kwok Wah grows up and cannot accept his mother's job. But soon he understands that she is respectable.
In high society there is a Madam Rose. Shum Chung-kei meets her and is enthralled. They begin dating. Kei knows very little about Rose. When Rose was little, her father Fok Wing-sum was betrayed by his business partner Shum Hung, who made him lose all his money. Hung was put in jail. Years later, when the Sino-Japanese war broke out, Hung reappeared as a spy. He arrested Sum. Although Sum escaped later, Hung caught his wife, who died later. Madam Rose wants to find Hung's offspring to take revenge. When she confirms that Kei is Hung's son, she approaches him. They are getting married. Kei invites his father to the wedding. Rose and Sum are anxious. However, Hung is alert and comes quietly. He discovers who Rose is and her motives. Rose and Sum go to Hung and they fight. Hung is guilty. He tries to jump off a cliff. Sum saves him. The enmity disappears. Kei and Rose stay together.
Scholar Yuen Man-lung leads a double life as Vigilante Golden Cat. Yuen is separated from his lover Tso Oi-lan by her snobbish father who promises her to Tsui Tai-fei, son of the magistrate and incriminates him as the wanted burglar. Yuen sneaks out of prison and wreaks havoc in Golden Cat's name; the exasperated magistrate has to release him. Before leaving for the imperial exams with the runaway Oi-lan, Yuen stages one final heist for his friend's sake. The officials trail Golden Cat to his house where his nocturnal costume is retrieved. His father is arrested as the criminal. Drawing a plan up her sleeves, Oi-lan's sister Oi-ling whisks the elder out of the execution ground. Despite failing at the exams presided over by corrupt examiners, Yuen saves the emperor on his homecoming journey, and returns triumphant as a duke.