在一个遥远的古代，宰相家中，有一位年事已高的老宰相，他再婚了，娶了一位名叫彩玉的小媳妇。彩玉年轻貌美，如花似玉，但她心中却常怀不满，因为她觉得自己被嫁给了一个老头子。
有一天，彩玉独自一人来到后花园散步，她在那里遇见了一位英俊的花匠。这两人一见钟情，但他们知道，他们之间有着无法跨越的障碍——年龄差距和身份上的隔阂。
为了解决这个问题，彩玉想出了一个主意。她告诉小花匠，他们可以利用宰相养的一只“朝鸟”来实现他们每天都能见面的愿望。这只鸟每天五更便会鸣叫，这让宰相能够提前上朝，而这段时间正好是彩玉和小花匠团聚的时候。
计划得逞，小花匠每晚四更就去捅醒那只朝鸟，让它提前鸣叫。当老宰相听到这突如其来的声音，便误以为是时辰到了，一气之下回到了府里。
第二天，是个月圆之夜，宰相决定把彩玉和小花匠召到后院的一个牡丹亭，以此为机会让他们表达自己的诗意。宰相吟诵道：“中秋之夜月当空，朝鸟不叫竹杆捅，花枝落到粉团上，干姜躲在门外听。”
小花 匠闻言 immediately realized he had been caught, and fell to his knees before the table, saying: "Eighteenth year of age accompanying an old man's wisdom, I am guilty of my mistake. Please do not blame me, sir."
Caiyu also knelt down and said: "The moon is in the west on this fine night, eighteen years young accompanying an ancient man. If you would lift your hand in kindness, a powder puff would perfectly match with flowers."
The old Prime Minister heard their words and burst into laughter. He knew that it was impossible for the young couple to be together under his roof. He finally agreed to let them leave the Prime Minister's residence and get married.
With gratitude in their hearts, Caiyu and the flower boy thanked him and left the mansion together.
