一个平静的下午，神色紧张的青年阿小（梁朝伟 饰）与老妖走进了一家银行，他们为高利贷所迫，计划打劫还债，然而老妖突然病发，阿小慌忙之下泄露歹意，不得不仓促上阵，打伤警卫，将银行职员与顾客扣押为人质。岂料在人质中，居然有一名警方重大通缉犯古何阳（狄龙 饰），古何阳曾击杀警察，为警方所恨之入骨，他本欲逃离港岛，眼下却不得不从阿小手中控制了银行的局面，闻讯赶来的警察们将银行团团包围，古何阳的老对手陈警官（梁家辉 饰）到场，试图与古何阳谈判换得和平收场，但警队众人只想将古击毙。被困的古何阳执意要求带狱中的女友（金燕玲 饰）一同逃走，但是女友真的出现时，紧绷的情势迅速发生了变化……本片翻拍自美国影片《热天午后》。

Miyako is a frustrated insurance saleswoman stuck in a major dry spell. She tries every trick in the book, including aggressive flirting, which gets her plenty of gropers but no buyers. One day while venturing down a narrow stairwell, she injures her ankle and happens upon Mitsuru who works for some mysterious foreign company. Decked out in high goth style -- complete with long inky black hair and mascaraed eyes -- Mitsuru cuts quite an odd figure, yet his seductive though menacing ways make him difficult for Miyako to resist. Escorting her to his office to treat her ankle, Miyako notices that his all-female staff seem more glassy-eyed and soul-deadened than the average office workers. In fact, they seem almost like zombies. Later, weird things start happening. Mitsuko finds vomit on her doorstep, she seems to be tailed by a shadowy woman in a red dress, and most strikingly, she finds herself utterly powerless against Mitsuru's advances. Soon she is offered a job at Mitsuru's office among the undead and the damned. Does Miyako's potential new place of employment at least offer stock options in exchange for her soul?

故事发生在上世纪七十年代的长江之畔。高中生星子（周韵 饰）与同在装卸站工作的陆粞（郭小冬 饰）朝夕相处，互生爱慕之意。当时正恢复高考，俩人商量共赴考场，但高考前夜陆粞因故退出，郁闷的陆粞醉酒后与同单位的水香（张帆 饰）发生了一夜情。星子如愿考上大学，她对陆粞的背叛非常生气，主动断绝了来往。陆粞非常后悔酒后的冲动，虽然新站长提拨了他，但他脑中始终挥不去星子的影子。星子后来与青年军官亦文（陈思成 饰）结合，但激情中她往往错把亦文当成陆粞，她深知她心中真正爱的仍是陆粞。然而，一切都无法挽回了，所有的思念都随着时间的逝去而消散了......

丈（余文乐 饰）是香港深水区的一名放蛇警察，作为底层的警察，丈整日与一个难得见光的世界打交道，这里充斥着暴力、毒品，是社会阴暗的一个角落。要想在这里生存，丈不仅要学会如何做警察，更需要学习黑道的生存法则，渐渐地丈的身份越来越模糊，他生活在黑与白之间的灰色地带。Lulu（冼色丽 饰）是这一区的妓女，丈与之保持着来往，却始终没有将关系向前推进。一次意外，丈误杀小头目四眼堂（廖启智 饰），神秘杀手（樊少皇 饰）是唯一目击者，为了自保，丈和神秘杀手展开了一场追逐……杀手背后有怎样的秘密？丈是否能够逃过此劫？《青苔》为我们展现了社会阴暗处的小人物们如何似青苔一般生存。