偷鸡盗狗 — “To engage in petty thievery or furtive, dishonest activities”

The idiom '偷鸡盗狗' (tōu jī dào gǒu), meaning to engage in petty thievery or furtive, illicit activities, is often associated with clandestine and dishonest actions.

In the classical Chinese novel 'Water Margin' (水浒传), the initial illicit affair between Ximen Qing and Pan Jinlian, facilitated by Wang Po, epitomized such furtive conduct. Their secret meetings and hidden transgressions were carried out in a manner akin to 'stealing chickens and pilfering dogs.' This covert wrongdoing eventually led to the murder of Pan Jinlian's husband, Wu Dalang, who was poisoned.

After Wu Dalang's death, Ximen Qing and Pan Jinlian no longer needed to carry on their affair 'like stealing chickens and pilfering dogs'; their illicit relationship became open and brazen. However, their open defiance ultimately led to their demise at the hands of Wu Song, Wu Dalang's brother, who avenged his brother's death.

The phrase thus captures the essence of underhanded, dishonest, and often petty illicit dealings.