The film opens with a car crash on Brooklyn Bridge, and introduces Henry Letham(Ryan Gosling), a survivor of the crash, sitting, unharmed, next to a burning car on the bridge.
Psychiatrist Sam Foster(Ewan McGregor)and his girlfriend(and former patient), art teacher Lila(Naomi Watts)are then introduced in a new scene. Sam discusses his patient, Henry, a college student and aspiring artist whom he describes as depressed and paranoid, with feelings of guilt and remorse over having “set fire to” his car at the beginning of the film. Henry mentions that he sometimes hears voices, and seems able to predict future events. Henry is also suspicious of Sam because he had suddenly been called to stand in for his ordinary psychiatrist, Beth Levy(Janeane Garofalo), Henry has told Sam of his plans to kill himself that Saturday at midnight, which Sam finds very troubling. Lila, who has survived a past suicide attempt offers to help to dissuade Henry from killing himself.
Sam investigates Henry's circumstances in an effort to help. After repeatedly attempting to reach Dr. Levy, he comes to her apartment to find her disoriented and lethargic, mumbling incoherent phrases like “I didn't touch him; I know you're not supposed to move them”, occasionally belittling Sam with maudlin reference to an implied unresolved tension between the two, and the fact that she's aware that he's citing an ex-patient. Henry, who had earlier claimed to have killed both of his parents, has his account contradicted by Sam when he finds Henry's mother(Kate Burton)and her dog living in a bare house, confused about Sam's identity(she insists that he is Henry)and refuses to respond to his questions. Henry's mother insists on feeding Sam, but when she opens the fridge it is completely empty. Her head starts bleeding and when Sam attempts to help her, her dog bites him.
At the clinic, whilst having his dog-bitten arm treated, Sam discusses the visit with a present police officer(Michael Gaston)who is curious as to why he would visit that house. Sam explains what happened, but the police officer tells him that he had attended the funeral for woman who lived there years ago. This seems to send Sam into a fugue in which the same scene and dialogue is repeated several times.
Later, Sam contacts a waitress named Athena(Elizabeth Reaser), whom Henry has mentioned that he had fallen in love with. She is an aspiring actress and he meets her at a script reading where she is reading lines from Hamlet with another man. She agrees to take him to Henry, but after a long trip down winding staircases he loses her. When he gets back to the rehearsal room, she is there reading the same lines as when he first met her.
The search continues until 11:33 pm on Saturday, less than half an hour before Henry plans to kill himself. At a bookshop known to have been frequented by Henry, Sam finds a painting that Henry had painted and bartered for books about Henry's favorite artist. He learns that the artist had killed himself on Brooklyn Bridge, on his twenty-first birthday. Henry's twenty—first birthday is Sunday, and Sam realizes that Henry plans to commit suicide on Brooklyn Bridge in imitation of the artist.
Sam finds Henry on the Brooklyn Bridge in a physical atmosphere that is increasingly unraveling. After failing to dissuade Henry, Sam turns away as Henry puts the gun in his mouth and pulls the trigger.
The car crash of the first scene is then reprised. Henry was fatally wounded in the crash but, in his last moments, is suffering survivor guilt. Each of the characters introduced earlier in the film was in fact a random spectator at the site of the crash, including Sam, a doctor, and Lila, a nurse, who treat Henry in an attempt to save him. The brief remarks they make are the same ones heard previously by their dream-world counterparts earlier in the film. They fail to rescue Henry, and Henry dies, but not before seeing Lila as Athena and proposing to her, which Lila accepts out of sympathy.
The entire film up until Henry's death had existed only in his mind — in his last moments...(a plot device used most famously in the short story An Occurrence at Owl Creek Bridge and also in the film Jacob's Ladder). However, there are clues that the people surrounding Henry as he lay dying were actually drawn into another world in some way. For instance, after Henry dies and is being loaded into a body bag, Janeane Garofalo's character is heard telling her name to the police: Elizabeth Levy. Since Henry died before hearing this, he would have no way of knowing how to “dream” her true name. Additionally, before parting, Sam appears to get a flash in his mind of the experiences between him and Lila that Henry had constructed, and asks Lila out for coffee.
电影以布鲁克林大桥上的一次撞车事故开头,介绍了亨利·拉萨姆(瑞恩·高斯令饰),事故的幸存者,他正毫发无伤地坐在桥上一辆燃烧的汽车旁边。
然后在一个新的场景里面,介绍了心理医生山姆·福斯特(伊万·麦克格雷格饰)和他的女朋友(也是他以前的病人),美术老师莱拉(娜奥米·沃茨饰)。山姆在讨论他的病人亨利,亨利是一个大学生,一个有抱负的艺术家,在山姆的描述中,他很沮丧并且类似妄想狂,他对于在电影的开始放火烧他的车子感到愧疚和懊悔。亨利提到,他有时候会听到一些声音,并且好像能够预知未来的事情。亨利也很怀疑山姆,因为他突然被叫来暂时代替亨利往常的心理医生贝丝·利维(詹尼安·吉劳法罗饰)。亨利告诉山姆,他计划在星期六午夜自杀,这让山姆觉得很麻烦。莱拉曾经企图自杀,但最终获救,她提出去帮助阻止亨利自杀。
为了帮忙,山姆调查了亨利的情况。在反复尝试联系利维医生后,他去了她的公寓,结果发现她精神错乱有些失常,含糊地说着像“我没有碰他,我知道你不应该移动他们”一类语无伦次的话,有时候她用两者之间含蓄而未解决的紧张的伤感话语来贬低山姆,事实是她知道他在和他的前病人约会。亨利先前声称他杀了自己的父母,但是山姆反驳了他,因为他在一间空旷的房子里面找到亨利的母亲(凯特·伯顿饰)和她的狗生活在一起,亨利的母亲对山姆的身份很困惑(她坚持认为他是亨利),并且拒绝回答他的问题。亨利的母亲坚持要给山姆做吃的,但是当她打开冰箱时,冰箱是空的。她的头开始出血,当山姆尝试去帮她的时候,她的狗咬了山姆。
当山姆在诊所里治疗他被狗咬伤的手臂时,他和一个对他为什么会造访那间房子感到好奇的现任警官(迈克尔·加斯顿饰)讨论了他的这次拜访。山姆解释了发生的事情,但是警官告诉山姆,他在几年前参加过住在那个房子里面的女人的葬礼。这好像将山姆带入了一个同样的场景、同样的对话重复好几次的神游之中。
接着,山姆联系了亨利提到过的一个他爱上的叫做阿西娜(伊丽莎白·里瑟饰)的女侍者。她是一位有抱负的女演员,山姆在一间排练室见到她,她正和另一个男人一起对《哈姆雷特》的台词。她答应带他去找亨利,但是在经过一段很长的螺旋状旋转楼梯后,他找不到她了。当他回到那个排练室的时候,她还在读和他刚见到她的时候相同的台词。
调查一直持续到星期六晚上11:33,距离亨利的自杀计划还有半个小时。在一个亨利经常去的书店里,山姆发现了一幅亨利画的画,并以此交换了关于他最喜欢的艺术家的书。他了解到这个艺术家在他21岁生日的时候,在布鲁克林大桥自杀了。亨利的21岁生日在周日,山姆意识到亨利打算模仿这个艺术家在布鲁克林大桥上自杀。
山姆在薄雾慢慢散开的布鲁克林大桥上找到了亨利。劝阻亨利失败后,山姆别过脸去,因为亨利把枪放进了自己的嘴,并且扣动了扳机。
接着又重复最开始的车祸镜头。亨利在碰撞中受了致命伤,但是在他生命的最后一刻,他内心充满罪恶感。之前介绍的每个角色,实际上都是车祸现场的一个随意的旁观者,包括山姆医生和莱拉护士,他们治疗亨利,尝试救他。他们进行的简短对话,和电影早期在他们的梦境世界里面对应人物先前听到的是一样的。他们没能救活亨利,亨利死了,但是,是在亨利将莱拉看成阿西娜并向她求婚,莱拉出于同情答应了他之后。
整部电影一直到亨利的死,都只是存在于他的意识之中——在他的弥留之际……(短篇小说《枭河桥记事》和电影《异世浮生》中用到的一个著名的情节设置)。然而,有一些线索显示,当亨利躺着濒临死亡时,周围的人实际上以某种方式被卷入到另一个世界。例如,当亨利死了并且被放进尸体袋时,詹尼安·吉劳法罗扮演的角色告诉警察她的名字:伊丽莎白·利维。由于亨利在听到这些之前已经死了,他将无法知道如何“梦到”她的真实姓名。此外,在离去之前,山姆似乎在他的意识中闪过亨利建立的他和莱拉之间的经历,并且约莱拉出来喝咖啡。