河内一个由兄妹四人组成的普通中产阶级家庭，大姐香与摄影师丈夫昆有一个儿子，但两人性生活不和谐，二姐卿（黎卿）同作家金结婚没多久，小妹琳（陈女燕溪）患有幽闭恐惧症，她与弟弟海保持着一种暧昧关系。在母亲的斋祀日，三姐妹追忆起被戏称为“母亲的谭”的神秘男人。 　　为获得写作灵感，金前往西贡寻找有关谭的资料，此时他发现梅已怀有身孕，不明白梅为什么要对自己保密，香在昆出差期间有了外遇，琳则在与海保持暧昧关系的同时，与另一个男孩有交往。透过平静生活的表面，三姐妹都有不愿人知的秘密和心事。With the brilliant Vietnamese summer as a setting Vertical Ray of the Sun is beautiful from beginning to end. The plot centres around three sisters, two of whom are happily married (or so it appears). The youngest sister is single and living with her cute older brother, whom she is desperately in love with. A second sister is married to a man who has another woman and child elsewhere whom he loves just as much as his wife -with a few conditions, she agrees to carry on with the marriage. The third sister and her husband are overjoyed to discover she is pregnant, and though he is tempted, her husband remains loyal to her. Charming, slow-paced, face value, family saga film.