十七岁的农村少年阿贵(崔林)在北京找到一份送快递的工作,因为得到许诺,当他赚到六百块时可以拥有公司暂借他用的银色变速越野车,他每日工作都很勤恳,可是就在梦想即将成真时,单车丢了,阿贵陷入绝望。 小坚(李滨)是和阿贵同岁的北京少年,但因家庭的贫困,他在维系骄傲时又常自卑。 父亲屡次三番将许下他一辆单车的承诺食言后,小坚为在同伴面前挣面子和泡马子(高园园),从家里偷来钱买了一辆二手车,不想此车正是阿贵所丢。阿贵发现他赖以生存的单车被小坚“盗”去后,开始不计代价拼命讨回,两个少年为守护自己的简单梦想发生争斗。Beijing: young men in packs, machismo, class divisions, violence, and indifference. Guei arrives from the country: toothbrushes, hotel foyers, and Qin, a rich neighbor in high heels, dazzle him. He gets a job as a messenger. The company issues him a bike, which he must pay for out of his wages. When it is stolen, Guei hunts for it. A student, Jian, has it; for him, it's the key to teen society - with his pals and with Xiao, a girl he fancies. Guei finds the bike and stubbornly tries to reclaim it in the face of great odds. But for Jian to lose the bike would mean humiliation. The two young men - and the people around them - are swept up in the youths' desperation.