On assignment in Thailand, French television journalist Marie Lelay (Cécile de France) is shopping for souvenirs for her lover's children. Back in a hotel room, her lover Didier looks over the balcony and witnesses the 2004 Indian Ocean earthquake and tsunami coming onshore; it hits as Marie watches from a distance. She runs away from the shore while trying to save a little girl, but they are both quickly swallowed by the wave. Pulled lifeless from the water, she is resuscitated by rescuers, but is left for dead. She gasps back to life after having a near-death experience in which she sees a vision of human figures inhabiting a realm of light, among them the silhouettes of the girl and her mother holding hands. Marie and Didier reunite in the aftermath of the disaster.
The story then turns to San Francisco where former professional psychic George Lonegan is persuaded against his wishes to perform a reading for Christos , a wealthy client of his brother Billy . A genuine medium with a gift for communicating with the dead, George abandoned his old career because he was unable to deal with the emotional impact of the reunions and the often disturbingly intimate family secrets revealed. While doing the reading, George hears the word June and asks if a date in June means anything to him. Christos at first denies that it means anything, but privately reveals to Billy that June was the name of his late wife's nurse, whom he was in love with for 10 years.
Billy pressures George to get back into the business of doing readings; he insists that George has a "gift" and an obligation to help people. George explains that his "gift" is actually a curse, and that the process is extremely painful for him.
In London, 12-year-old twins Marcus and Jason try desperately to prevent social services from taking them away from their mother, Jackie , a heroin addict. After evading the authorities yet again, Jackie sends Jason to the chemist to pick up her detox prescription. On the way home, Jason is attacked by street thugs, and while trying to escape, he is hit by a van and killed.
Marie returns to Paris, her experience, however, interferes with her work to the point that Didier, who is also her producer. sends her on a leave of absence to write the book they've discussed, which would add to her prestige.
George enrolls in a cooking class taught by one of San Francisco's leading chefs. Its students are paired-up, resulting in George being partnered with a young woman named Melanie . The two soon hit it off. He returns to his apartment when confronted by a neighbor of Christos. She begs for him to perform a psychic reading in order to talk to her baby again but he refuses.
No longer able to protect his mother, and barely able to cope with life without the brother he idolizes, Marcus is sent to a foster home.
Marie sells her idea of a new book and receives complete backing for the book. She celebrates by going to dinner and asks her lover what he thinks happens when they die. He answers that its "lights out" and nothing else. Marie believes that there may be a hereafter where there is life on the other side.
After attending their second class, George and Melanie decide to put their new culinary skills to use by preparing an Italian dinner at George's place. All goes well until they hear an ill-timed phone message from his brother, which inclines George to reveal his past as a psychic to Melanie. He explains how he fell ill as a child and that during surgery to save him, he suffered brain damage which left him with migraines and the psychic ability, which doctors diagnosed as a form of schizophrenia. He has medication to stop the visions, but does not take it because it robs him of the ability to feel anything. Curious, she presses George to do a reading for her. George explains his reluctance, since he knows it will destroy any chances for a relationship between them. Melanie is insistent, however, and George acquiesces. They contact the spirit of Melanie's mother and father, who ends the session by asking her forgiveness for what he did to her as a child. Melanie flees George's home in tears. Saddened, George toys with the idea of taking the medication but instead just deals with his sadness and difficulty with sleeping by listening to audiobook versions of Charles Dickens novels as read by Derek Jacobi.
Marcus moves in with his foster family but still does not speak to anyone. He is distant at school and barely does much of anything.He becomes hopeful that there is some way to talk to his brother again.
Now writing a book and with more time to contemplate her near-death experience, Marie travels to Switzerland to meet a renowned specialist in the field. As the director of a hospice who has seen her share of dying patients, the doctor describes herself as a former atheist who was convinced by evidence experienced by Marie through her patients that the afterlife exists and that people like Marie have had a genuine view of it. She persuades Marie to write a book on her experience in the hope that the scientific community will ultimately accept the reality of life beyond death.
George is laid off from his factory job, and is persuaded by Billy to revive his psychic practice. At the next cooking class, Melanie does not show up.
Desperate for one last reunion with his twin brother, Marcus steals money from his foster parents and goes around London seeking psychics to help him contact Jason. Most of the mediums he encounters are either outright fraudsters, or their methods don't work. While he is trying to board the underground at Charing Cross, Jason's cap, which has become a talisman for Marcus, blows off his head. Delayed by trying to find the cap, he misses his train and sees it explode in the tunnel during the 2005 London Bombings.
Having been in talks with a publisher before her trip to Thailand about a biography of François Mitterrand, Marie now stuns them with her new manuscript entitled "Hereafter: A Conspiracy of Silence". The publisher rejects the manuscript, insisting that his company only publishes books with political themes and that her switching the content is unacceptable. Marie leaves her office humiliated.
Later that evening at dinner with Didier, Marie recounts her humiliation at the publisher's office, lamenting that she should just write her book as a hobby on her own time and return to work at the television show. Didier is evasive and Marie learns that he does not intend on having her back at the job from which he urged her to take leave, claiming her public interest in the hereafter damages her reputation as a serious journalist. Stunned and hurt, she asks if he is having an affair with the woman who has replaced her on the TV news program. He responds with telling silence, and she abruptly leaves the restaurant. Just as she arrives, totally dejected, back at her apartment, the publisher calls to tell her that he knows of two publishers who would be interested in her book. She sends out manuscripts to the two publishers the next day.
Still convinced that his ability is a curse, George abandons Billy and his plans for a psychic business and leaves San Francisco for London. There, he visits the Dickens House and learns of a live reading of Dickens by Derek Jacobi that same day at the London Book Fair. While there, he meets Marie who is at the fair promoting and signing her book. Hereafter. While handing a signed copy of her book to George, their hands touch and George has a psychic flash of Marie's near-death experience.
Marcus and his foster parents are also at the London Book Fair to meet their older son. While there, Marcus spots George whom he remembered back from when he was searching for psychics online. Marcus attempts to speak with George, who brushes him off and returns to his hotel. Undeterred, Marcus follows him back and stands vigil outside his window until George eventually agrees to do his reading.
Through George, Jason tells Marcus that he is happy in the afterlife. He instructs Marcus to stop wearing his cap and says that is why he knocked it off his head at the train station, which had the side effect of saving him from the bomb. Jason tells Marcus he must now stand on his own but not to fear this "because we are one". Marcus later visits his mother in a rehabilitation center. She is visibly better, and he is not wearing Jason's cap.
As compensation for helping him, Marcus lets George know where Marie is staying. George visits the hotel and leaves an anonymous note for Marie, saying he believes her book to be true. She decides to join the anonymous fan for lunch and discovers George. While she is looking for him, George sees a vision of them kissing at the same meeting. The film ends with the two just sitting down to talk.
