The film revolves around an elementary school teacher, Anna Taylor (Christina Ricci), who is unhappy with her life. She has a selfish, unloving mother, Beatrice (Celia Weston), and a boyfriend, Paul Coleman (Justin Long), who can't seem to figure her out. The film opens as a corpse is in the process of being prepared for a funeral; the man preparing the corpse speaks to it mysteriously, but cheerily. He takes a photo, and the scene fades. Anna is introduced along with Paul, as they finish having sex. She appears unaffected and cold, while he is frustrated with her disinterest. Later, after school, a young boy she teaches, Jack (Chandler Canterbury), asks her as she as leaving to the funeral , if he could come along. He says his mother, who had neglected to pick him up from school, would not mind. Confused, she attempts to explain that funerals are a personal occasion. Jack offers that he has never been to a funeral before, but she insists it would be inappropriate. The funeral is revealed to be for her recently deceased music teacher, the corpse from the initial scene. There, Anna encounters the solemn owner of the funeral home, Eliot Deacon (Liam Neeson). One night, Anna meets Paul for dinner, not realizing he is going to propose to her and ask her to move to Chicago with him for a job promotion. Paul begins ambiguously, so Anna assumes the worst. Before Paul has a chance to explain, she panics, thinking he's breaking up with her. After a short argument in the restaurant, Anna storms out and drives off passionately. She has an accident while trying to use her cell phone and drive in the rain, while a mysterious white Van is seen on the road alongside.
Anna wakes up dazed, confused, and numb. She finds the morgue director, Eliot, cleaning her wound and telling her she has died. He appears frustrated with her, explaining that all dead people claim to be alive just because they, "breathe and piss and shit." He tells her he has a gift, to assist the dead crossing over; to help them accept their deaths. Later in the funeral home, Eliot is revealed to have a collection of photographs of corpses, it is implied that he helped each to cross over, and speaks to them, implying a level of mental instability. Unwilling to accept her potential death, Anna clings onto life. Eliot injects her regularly with a chemical to "relax the muscles and keep rigor mortis from setting in." Paul, unable to fully accept her death, asks Eliot if he could see her one last time; however, Eliot cannot, by law, show the body to anyone but family. Paul becomes quite angry, but leaves. Attempting to gain access to her, he pleads with friends in the police, who are sympathetic but unwilling. Anna is revealed not to have been taken to a hospital, rather pronounced dead at the scene and shipped to the funeral home. At an unknown funeral service, Eliot encounters Jack. They speak for a moment, during which Jack admits he had thought the funeral had been for Anna. As she still grapples with the concept of her own death, Anna attempts to escape several times but is unsuccessful; Eliot tells her she must let go of life, she had not really been living anyway. Eventually, she steals Eliot's keys, escapes, and finds a room with a phone, intent on calling Paul for help. Paul is unable to hear her properly and hangs up thinking it's a prank. Anna finally accepts she's dead, when Eliot allows her to look at herself in the mirror. She is horrified to find she looks like a corpse. Outside, Eliot spots Jack, gazing up at Anna. In a scene in his home, Jack's apparently negligent mother is shown to be sitting with a grotesque appearance, staring at the television set. At school he tells Paul he saw Anna, which sends Paul into a rage, hitting the boy. Upon confronting Eliot, Jack is told he has the same gift: the ability to see those between life and death as they really are. Eliot tells the boy that the first person he saw was his mother, alluding to Jack's ambiguously stoic mother. Over time, Paul becomes ever more paranoid as to whether or not Anna really is dead; he becomes suspicious of Eliot.
During the final preparation for the funeral, Anna asks Eliot if she can see herself one last time in the mirror. Eliot holds up a small mirror, but while she stares at herself, she takes a deep breathe and notices her it condense on the glass. Suddenly concerned that Eliot has been lying to her, she begins to believe she has been alive all along. Disappointed that she had come so close to accepting her death yet failed, Eliot grimly injects her one last time with chemicals to make her numb. In the graveyard while digging Anna's grave with Jack, Eliot explains that there are many corpses walking around with "no life left inside them," and because only they can see them, it is their responsibility to help them into the grave. It is never revealed whether this is metaphorical or literal.
After the funeral, Paul drinks heavily, telling Eliot he knew Anna wasn't dead. Anna is shown awakening while being buried. Trying to cry out and open the coffin, she struggles against death. As she slowly dies in the coffin, Eliot offers that Paul should go to the cemetery and find out whether Anna is actually dead or not, before it's too late. Paul rushes to the cemetery, driving under the influence and speedily. There is another ambiguous cut before he is shown to have dug up Anna's grave, to find her alive. They embrace and Anna tells him "she has always loved him." Paul then sees a flash of light and wakes up in the morgue with Eliot preparing his body. He says he saw Anna and Eliot tells him he never made it to the cemetery due to a car accident that killed him. It is left fully ambiguous whether Eliot is telling the truth, or simply a serial killer; but it's pretty obvious that he perpares death for those who did not appreciate life. Jack is shown to have become his protege. Paul claims just as vehemently as Anna that he is not dead, as they begin preparing his body.
