半尺（陈少霞 饰）从小生活在一个远离城市的小岛上，这里区别于都市的喧嚣，常住于此的半尺也向往城市的热闹，因此她最期待的就是夏天。每到夏天就会有来自城市的年青人造访这座岛度假，这些人中各有各的心事各有各的秘密。这一年的夏天，半尺那早就离开小岛去香港工作生活的哥哥阿伟（梁朝伟 饰）突然回到小岛，手臂上还带着伤痕，多年不见的兄妹俩有了不少隔阂，哥哥的心事成了半尺最想知道的秘密。不久，半尺发现在这群游客中有一个独来独往的女人（叶玉卿 饰），她成熟而有风韵不同于那班年轻学生，每次来岛上都不与别人交谈。终于一天，半尺发现这个神秘的女人竟然是为了哥哥而来……

Three Summers opens, a young man with a difficult past leaves his present home in the city of Hong Kong and hearkens back to the fishing village of his youth. Against the backdrop of that locale, his young sister has recently befriended a group of adolescents who visit the isle perennially - every summer - and who share their individual stories with her. One tale at a time, she begins to experience life vicariously through the others' recollections.