天水围的中学生何灵杰（邓德保 饰）生活在一个问题家庭：母亲精神有障碍，父亲嗜赌又暴力，弟弟两年来下落不明。警方突然到学校拜访何灵杰，带来了弟弟何俊杰（黄溢豪 饰）杀人后又自杀未遂的消息。古惑仔拗柴令人威胁何灵杰交出弟弟偷走的毒品，何灵杰由此与弟弟的同伴白木和鸡子结识。在纷乱的校园中只顾读书的何灵杰从来不曾为遭受殴打的弟弟出头，弟弟离家后的两年中过着怎样的生活他也一无所知。何灵杰拜访白木和鸡子，打听弟弟的经历，原来当年在街头游荡的何俊杰偶然结识白木等人，不甘再次受辱的俊杰奋起反抗，反而与白木一伙结为朋友。从此这班天水围少年入室偷窃、纵情狂欢，直到某日古惑仔拗柴将他们纳入了自己的势力。俊杰在童党混乱的生活中渐渐迷失，慢慢向未知深渊滑落…

Ling-Kit HO is just like one of many other students in Tin Shui Wai. However, he is a lot more hard-working than all the others as he wants to get away from this besieged city. Apart from his study, he is indifferent to everything because he comes from a defunct family. Having to take care of his mentally-ill mother, Ling Kit is also forced to face his Dad – a heavy drunker and a heavy gambler. His younger brother Chun-Kit has left the family for years. At that time, Chun-Kit was heavily bullied by his classmates in school and he was always beaten by his drunken father. Being the elder brother, however, Ling-Kit did not protect Chun-Kit from being beaten so Chun-Kit left in great panic.

Ti Shui Wai aussi connu sous le nom de “Besieged City” (littéralement “Cité de la tristesse”) est la principale banlieue réputée à problèmes de Hong-Kong. Ling-Kit Ho y habite au beau milieu de plus de 270 000 habitants. Ling n’ayant plus de nouvelles de son petit frère, Chun-kit, depuis 2 ans, apprend qu’il est dans le coma après une tentative de suicide. Chun-kit est aussi accusé de meurtre. Sans avoir le temps de digérer la nouvelle Ling est enlevée par Occha qui lui demande de retrouver une importante quantité de drogue, soit disant dérobée par son frère.

모범생인 링지에는 정신병을 앓고 있는 어머니와 도박에 빠져 폭력을 일삼는 아버지와 함께 살고 있다. 어느 날 2년 전 집을 나가 소식이 없던 남동생 준지에가 살인혐의를 받고 있으며, 현재 혼수상태라는 소식을 경찰이 들고 링지에를 찾아오는데...