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.
電影以布魯克林大橋上的一次撞車事故開頭,介紹了亨利·拉薩姆(瑞恩·高斯令飾),事故的幸存者,他正毫發(fā)無傷地坐在橋上一輛燃燒的汽車旁邊。
然后在一個新的場景里面,介紹了心理醫(yī)生山姆·福斯特(伊萬·麥克格雷格飾)和他的女朋友(也是他以前的病人),美術(shù)老師萊拉(娜奧米·沃茨飾)。山姆在討論他的病人亨利,亨利是一個大學生,一個有抱負的藝術(shù)家,在山姆的描述中,他很沮喪并且類似妄想狂,他對于在電影的開始放火燒他的車子感到愧疚和懊悔。亨利提到,他有時候會聽到一些聲音,并且好像能夠預(yù)知未來的事情。亨利也很懷疑山姆,因為他突然被叫來暫時代替亨利往常的心理醫(yī)生貝絲·利維(詹尼安·吉勞法羅飾)。亨利告訴山姆,他計劃在星期六午夜自殺,這讓山姆覺得很麻煩。萊拉曾經(jīng)企圖自殺,但最終獲救,她提出去幫助阻止亨利自殺。
為了幫忙,山姆調(diào)查了亨利的情況。在反復(fù)嘗試聯(lián)系利維醫(yī)生后,他去了她的公寓,結(jié)果發(fā)現(xiàn)她精神錯亂有些失常,含糊地說著像“我沒有碰他,我知道你不應(yīng)該移動他們”一類語無倫次的話,有時候她用兩者之間含蓄而未解決的緊張的傷感話語來貶低山姆,事實是她知道他在和他的前病人約會。亨利先前聲稱他殺了自己的父母,但是山姆反駁了他,因為他在一間空曠的房子里面找到亨利的母親(凱特·伯頓飾)和她的狗生活在一起,亨利的母親對山姆的身份很困惑(她堅持認為他是亨利),并且拒絕回答他的問題。亨利的母親堅持要給山姆做吃的,但是當她打開冰箱時,冰箱是空的。她的頭開始出血,當山姆嘗試去幫她的時候,她的狗咬了山姆。
當山姆在診所里治療他被狗咬傷的手臂時,他和一個對他為什么會造訪那間房子感到好奇的現(xiàn)任警官(邁克爾·加斯頓飾)討論了他的這次拜訪。山姆解釋了發(fā)生的事情,但是警官告訴山姆,他在幾年前參加過住在那個房子里面的女人的葬禮。這好像將山姆帶入了一個同樣的場景、同樣的對話重復(fù)好幾次的神游之中。
接著,山姆聯(lián)系了亨利提到過的一個他愛上的叫做阿西娜(伊麗莎白·里瑟飾)的女侍者。她是一位有抱負的女演員,山姆在一間排練室見到她,她正和另一個男人一起對《哈姆雷特》的臺詞。她答應(yīng)帶他去找亨利,但是在經(jīng)過一段很長的螺旋狀旋轉(zhuǎn)樓梯后,他找不到她了。當他回到那個排練室的時候,她還在讀和他剛見到她的時候相同的臺詞。
調(diào)查一直持續(xù)到星期六晚上11:33,距離亨利的自殺計劃還有半個小時。在一個亨利經(jīng)常去的書店里,山姆發(fā)現(xiàn)了一幅亨利畫的畫,并以此交換了關(guān)于他最喜歡的藝術(shù)家的書。他了解到這個藝術(shù)家在他21歲生日的時候,在布魯克林大橋自殺了。亨利的21歲生日在周日,山姆意識到亨利打算模仿這個藝術(shù)家在布魯克林大橋上自殺。
山姆在薄霧慢慢散開的布魯克林大橋上找到了亨利。勸阻亨利失敗后,山姆別過臉去,因為亨利把槍放進了自己的嘴,并且扣動了扳機。
接著又重復(fù)最開始的車禍鏡頭。亨利在碰撞中受了致命傷,但是在他生命的最后一刻,他內(nèi)心充滿罪惡感。之前介紹的每個角色,實際上都是車禍現(xiàn)場的一個隨意的旁觀者,包括山姆醫(yī)生和萊拉護士,他們治療亨利,嘗試救他。他們進行的簡短對話,和電影早期在他們的夢境世界里面對應(yīng)人物先前聽到的是一樣的。他們沒能救活亨利,亨利死了,但是,是在亨利將萊拉看成阿西娜并向她求婚,萊拉出于同情答應(yīng)了他之后。
整部電影一直到亨利的死,都只是存在于他的意識之中——在他的彌留之際……(短篇小說《梟河橋記事》和電影《異世浮生》中用到的一個著名的情節(jié)設(shè)置)。然而,有一些線索顯示,當亨利躺著瀕臨死亡時,周圍的人實際上以某種方式被卷入到另一個世界。例如,當亨利死了并且被放進尸體袋時,詹尼安·吉勞法羅扮演的角色告訴警察她的名字:伊麗莎白·利維。由于亨利在聽到這些之前已經(jīng)死了,他將無法知道如何“夢到”她的真實姓名。此外,在離去之前,山姆似乎在他的意識中閃過亨利建立的他和萊拉之間的經(jīng)歷,并且約萊拉出來喝咖啡。