梦想成为摄影师的男主角円人,和实现了模特梦想的青梅竹马弥生突然开始同居的故事。原本关系渐行渐远的两人,在夜晚的"玩耍"中开启了全新的关系。弥生似乎还有一个无法对円人说出口的秘密。从青梅竹马到恋人,究竟两人的感情会迎来怎样的发展呢?

　　This long-lost masterpiece of hardcore gay erotic cinema centers on a handsome young stud who rides his motorcycle through myriad sexual encounters, from a soccer game’s locker room to a phantasmagoric and deeply melancholy orgy. A labyrinth of all-male fantasies whose outstanding beauties always end up fading away while leaving their sensual protagonist dealing with his own loneliness, EQUATION was directed with supreme grace by the mysterious Dietrich de Velsa (aka Francis Savel/Frantz Salieri). A former painter, de Velsa was also the owner and artistic director of La Grande Eugène, one of the first drag cabarets in Paris. Years later, he collaborated with Joseph Losey on MR. KLEIN (1976) and DON GIOVANNI (1979). His one and only film, EQUATION TO AN UNKNOWN stands as one of the most extraordinary erotic films of all time.
　　“The most melancholic porn film I’ve ever seen. It’s very sad, and aesthetically beautiful. Just a young man wandering through several depictions of love and choreographies of love-making; it’s like a ceremony, a ceremony of fantasies, especially the last sequence where the main character recalls all his previous fantasies, which come one by one around his bed and make love to him. I think it’s one of the most beautiful film sequences of French cinema.” –Yann Gonzalez

一部以大陆家庭为背景的伦理惨剧，麦惠芳(钟淑慧饰)虽是生长在一健全的家庭内，但她的家人却全都不当她是家中的一分子，还对她呼呼喝喝，又以她的后父麦泉(何家驹饰)更甚，一次更乘着酒意把她强奸了。惠把此事告诉其母，但她却无动于衷，惠只好离家投靠其男友小健(吴岱融饰)处。

健是位严正的公安，对惠关怀体贴；惠怕被嫌弃，惟有把事件隐瞒。可是惠的后父麦食髓知味，更以强奸时所拍下的裸照作威胁，迫惠再次就范。惠深知这不是办法，遂持刀迫麦把底片交还，惜无法得逞，反而被麦再次强奸。健赶至见状，惊怒下开枪把麦击伤，纠缠中更被击晕。为免健遇害，盛怒下的惠拾枪把麦枪杀，并把母亲及一众弟妹逐一杀掉，健醒来知一切已无法挽救，只默然把所有指纹抹掉。

然惠往公安局自首，公安(黄秋生饰)虽知惠是元凶，然而望着楚楚可怜的惠，觉得判这个女人杀人有罪，是否一个恰当的判决呢？

阿惠(钟淑慧饰)是家中的养女，因此每日过着寄人篱下的压抑生活，某日，养父阿麦(何家驹饰)喝醉了酒，在醉意朦胧之中，他竟然丧尽天良地将阿惠强暴。受辱后的阿惠在家中孤立无援，便想到了男友阿奇(吴岱融饰)，然而，看到阿奇深爱自己的样子，于心不忍的阿惠选择了隐瞒实情。强暴事件之后，阿麦对于阿惠的骚扰变本加厉，他以阿惠的裸照相威胁，两人纠缠之际刚好被阿奇看到。愤怒的阿奇开枪打伤了阿麦后被击晕。愤怒之中，阿惠拾起枪将全家人杀死，后前往警局自首，将一切罪过揽到了自己身上，然而，接待她的警察在得知了实情之后对阿惠动了恻隐之心。