The movie opens with a shot of a ferry unloading at Cape Cod. As the cars disembark, it is apparent that the driver of a BMW SUV has not returned to their vehicle. The car is eventually towed from the ferry. There is a shot of a body washing up on a beach.
The action cuts to London. An unnamed writer (Ewan McGregor) is having lunch with his American agent, who is convincing him that he is the perfect candidate to ghostwrite the memoirs of Adam Lang (Pierce Brosnan), the former British Prime Minister. He explains that the previous ghostwriter, Mike McCarra, a close friend of Lang, was found washed up on a beach in Cape Cod, a presumed suicide. He left behind a full manuscript, but it needs polishing. After his agent convinces him, the writer (referred to only as "The Ghost", "The Ghost Writer," or "Man" by Adam Lang) agrees to meet with Adam Lang's lawyer and publisher to discuss the position.
Cut to the Ghost turning up at Rhinehart Publishing to discuss the book. The editor, who has a past relationship with the Ghost, tells him he doesn't think he is right for the job, but the Ghost makes a good impression on Lang's lawyer and publisher (both Americans) by explaining that he is does not normally ghostwrite political memoirs, which is why he is the right candidate for the job - he will write the book the public want to read. He is hired and it is agreed that he will fly that evening to Cape Cod to meet with Adam Lang and read the rough manuscript left behind by Mike McCarra. As he is leaving the meeting, Lang's lawyer hands him a manuscript in a plastic bag. The Ghost asks if this is "the" manuscript - of Lang's book. The lawyer says no, that it is the manuscript of the memoirs of another client of his, which he would like the Ghost to take a look at.
The Ghost takes a cab home from the meeting. As he gets out of the cab in front of his house, a couple approaches him on a motorbike. The passenger on the bike gets off the bike, punches the Ghost in the stomach, steals the manuscript in the plastic bag, and takes off. The Ghost phones his agent and says he is in shock and cannot fly to Cape Cod tonight. His agent informs him he has negotiated a salary of $250,000 if the Ghost can finish the memoirs in four weeks. This is an unheard of salary for the Ghost and he departs for Heathrow.
We next see the Ghost sitting in a first class lounge watching the news, which reports that "leaked documents" have revealed that Lang handed over prisoners of war to the CIA, who tortured the detainees using water boarding. The former British Secretary of State, Robert Rykert, a friend and colleague of Lang's, is interviewed, saying that he could not, in all good conscience, keep the information that was leaked to him to himself and so went to the media. He has essentially "double crossed" Lang, who appointed him as Secretary of State when he was Prime Minister. The Ghost calls his agent in disbelief and explains he can't possibly write Lang's memoirs now. His agent reminds him of the money and he agrees to go.
We see a number of travel scenes where the Ghost takes several flights, a ferry and a car to reach Adam Lang's compound in Cape Cod. The weather is horrible, as it is January. The house is modern and austere, glass and steel. The Ghost is greeted by Adam Lang's assistant, Abigail Bly (Kim Cattrall), who invites him into the house. We can hear a woman screaming and crying. This is Ruth, the wife of Adam Lang. "It's not a good day," Abigail explains with a tight smile.
Abigail takes the Ghost to an office in the house, where she uses an electronic card to open a safe, showing him the manuscript of the memoirs, and a memory key, which contains the transcript. She tells him the manuscript may never leave the room. She tells him that Adam is in Washington, but will be returning later than evening, and that he should read the manuscript before then. The Ghost tries to flirt with Abigail several times but she tells him she is married and he immediately turns off the charm. The Ghost puts his feet up to read, and realizes that the manuscript is poor and will require heavy revision. He falls asleep halfway through reading the manuscript but is woken up by a staff member who brings him lunch. He stares out the window of his office onto the beach, and sees Ruth, Adam's wife, walking along the beach. He goes outside to join her.
As they walk, it becomes clear that Ruth (Olivia Williams) is a strong, opinionated woman in her own right. She tells the Ghost that it was her idea to have him write Adam's memoirs, as she had read his previous work and found it entertaining. They return to the house in time to find Abigail and her entourage leaving for the local airport to pick up Adam, who is arriving by private jet. Ruth decides to go along, and with a snarky remark tells Abigail she can "stay home and do her nails." Abigail says she will go in the "backup car." Ruth tells the Ghost he should come along "to say hello" to Adam.
We see the small party waiting in the wind at the airport for Adam's private jet, a Hatherton jet, to arrive. Adam is good looking and smarmy. He barely notices the Ghost, until he is informed by Ruth that he is "Mike McCarra's predecessor." Adam looks grieved at the loss of Mike. After some initial interviews with Adam, the Ghost is taken back to his hotel, where he is the only guest. Late at night, in the hotel bar, he gets drunk while watching CNN news coverage of Adam and the leaked torture documents. He asks the bartender to change the channel and watches hockey. He is approached by the only other man in the bar, who asks him if he heard that Adam Lang was on the island. The Ghost plays dumb and says he doesn't know anything about that. The man calls the Ghost an asshole, and disappears. Later, when the Ghost gets back to his room, the door is open and he realizes someone has searched through his things.
The next day, the Ghost awakes to find the parking lot of the hotel filled with media. His phone rings, and Abigail informs him he must check out of the hotel and move into the beach house in order to finish the memoirs. The torture documents story has broken and "the game has changed," according to Abigail. The Ghost reluctantly packs his things; he remarks that he does not stay with clients.
Back at the desolate beach house, the Ghost begins to interview Adam. He asks him about when he got into politics. Adam explains that he had no interest in politics for much of his life, and abhorred student politicians at Cambridge. However, he explains that one weekend morning in 1977, when he was still sleeping, hung over from partying the night before, someone knocked persistently on his door. He opened it to find Ruth, an Oxford scholar who was campaigning for the Labour Party. He fell in love with her, he explains, and that was when he joined the Labour Party. The Ghost is charmed and says this should be the opening of the memoirs.
He also asks Adam about his acting. He was renowned at Cambridge as an actor, and a member of the Cambridge Footlights drama group. Adam is offended by this line of questioning. He says that his was often criticized when he was Prime Minister and called "an actor" and refuses to discuss acting in his memoirs. He has a bit of a tantrum, and the Ghost suggests that they take a break.
Later, Adam apologizes lamely to the Ghost for his outburst. He had just received a call from Robert Rykart that the International Criminal Court (the iCC) at The Hague would officially be investigating him for war crimes based on the leaked documents, which Rykart publicized. Lang's entire team goes into crisis mode, and the Ghost sits in on a meeting with Adam's lawyers, Ruth, Abigail and Adam. They are watching CNN, where the coverage is 24-hours on Adam and the International Criminal Court. Adam's lawyer says that Adam should not travel anywhere where the jurisdiction of the ICC is recognized, which limits him to the United States, China, Iraq, Iran and a few other African countries. Ruth is crying and says that this means they cannot go home to London. Adam's lawyer says he should go to Washington and be seen in high profile meetings with the President on global issues, to show it is "business as usual." Ruth remarks that this will do nothing to dispel the image that as Prime Minister, he was a puppet for the Americans. Adam asks Ruth what she thinks he should do. It is clear her opinion means a lot to him. She says he must go back to London to show that he has nothing to hide. Abigail points out that CNN has just reported, "Britain will cooperate fully with the investigation." Adam says "Washington it is then." He tells Abigail to get the team ready to go, and to pack a bag for herself and him. It is suddenly clear to the Ghost that Abigail and Adam are having an affair, and that Ruth is aware of it. Ruth leaves the room, slamming the door.
We see Adam, his lawyers, and Abigail leaving for the airport, to head for Washington. As they head out of the gates of the compound, they are greeted by protesters, including the grey haired man from the hotel, who says that he was in the British military for 30 years, and that his son followed in his footsteps, but was killed in Iraq, for which he blames Adam Lang, who he calls a murderer. Adam makes a bland statement about his innocence and disappears.
The Ghost is not sure what to do now. He retires to his new room, which used to belong to Mike McCarra. It is still full of Mike's things, and the Ghost starts emptying the closet get rid of Mike's things. As he pulls out a drawer, he finds an envelope taped to the drawer. He opens the envelope and finds pictures of Adam from his Cambridge dramatics days, and the name of one of the other people pictured, Paul Emmett, circled. The Ghost turns to a page in Adam Lang's memoirs, which mentions Paul Emmett, a reference that he remembered. There is also a phone number written on the back of the picture. The Ghost calls the number, and Robert Rykart answers. The Ghost is spooked and immediately hangs up. Robert Rykart starts to continually call the Ghost back, and the Ghost ignores the call. The Ghost also finds in the package Adam Lang's Labour party membership card, which is dated 1975. This directly contradicts Adam's earlier story that he had joined the party in 1977, when he met Ruth.
The Ghost heads out on a bike to explore the island. He gets caught in a rainstorm, and goes to a local house for shelter. An old man opens that door and says, "You're British, aren't you?" The Ghost confirms this. "He was too," the old man says. "Who," asks the Ghost? "Mike McCarra." The Ghost explains he is his predecessor. The old man tells the ghost that he knows the currents around the island and there is no way that McCarra's body should have washed up where it did, on the west side of the Island, if he jumped off the ferry. He also says that Mike said he had uncovered something, which was "in the beginnings" of the memoirs. The Ghost thinks this means the beginning of the memoirs, dealing with Adam's Cambridge days, which are the subject of the photos he found. The Old Man also tells the Ghost that a local woman saw flashlights on the beach, confirming to the Ghost that Mike McCarra's death is suspicious. The Ghost asks where he can find the woman, to talk to her. The old man tells him that the woman "fell down the stairs" and has been in a coma for a week. The Ghost is thoroughly spooked.
Later, on the beach, he meets with Ruth and her security guard. They have come to look for him. They return to the house, and Ruth invites him to have dinner with her. At dinner, the Ghost asks Ruth why she herself never went into politics. She bitterly says she wanted to do so. The Ghost tells her that he believes Mike's death was suspicious. Ruth begins to cry and says she believes so as well. She also says that Mike said that "it was all there in the beginnings" of the memoirs. She heard Adam and Mike get into a huge fight the night before Mike died. She picks up the phone to call Adam, and then decides not to call. She says she is going for a walk on the beach, and that the Ghost should not wait up.
Later, the Ghost is awoken by Ruth, who is in tears. She comes into his room wearing only a bathrobe, and pretends to be vulnerable and in need of comfort. She says how upsetting it is for her, when Adam used to rely on her to help him make decisions, and now he does not, and has clearly hidden things from her, such as his fight with Mike McCarra. It is clear that she is playing a game. The Ghost knows this as well, but succumbs to her and they have sex.
In the morning, the Ghost packs his things and says he cannot stay in the house any longer. He hops in the SUV the Langs reserve "for guests" (the same SUV that Mike McCarra drove onto the ferry and abandoned), and drives away. The GPS in the SUV is set on a particular route, set by the previous driver, McCarra, and although the Ghost is trying to return to the hotel, he cannot turn off the GPS, and finally gives in and decides to take the route, which the GPS has suggested. It takes him to the ferry, onto the mainland, and through Boston.
Following the GPS, the Ghost arrives at a gated compound in the forest, surrounded by security cameras. He checks the mailbox, and realizes he is at Paul Emmett's house. He uses the intercom to gain entrance to the house to speak to Paul Emmett (Tom Wilkinson). Emmett, a Professor at Harvard, and the Chairman of a think tank called the Arcadia Group, is pleasant but asks the Ghost what he wants. The Ghost explains that he is writing Adam Lang's memoirs. Emmett says he does not know Lang. The Ghost says that he thinks that this is not true, and shows Emmett the Cambridge pictures, clearly showing the two of them together. Emmett continues to explain away the connection. The Ghost then shows Emmett the page of Adam's memoirs in which Emmett is mentioned. Emmett continues to deny that there is any connection between Emmett and Adam other than a passing acquaintance. The Ghost pushes further by saying that he knows that Mike McCarra drove up to visit Emmett, and died on the ferry back to Cape Cod. Emmett denies meeting McCarra and escorts the Ghost out of his house, telling him to turn right instead of left, "otherwise you'll go deeper into the forest and never be heard from again."
The Ghost pulls out of Emmett's driveway and notices a black sedan waiting for him. The car follows him, and he panics, eventually pulling into a wooded lane in order to evade them. When he gets to the ferry terminal, he dawdles to ensure he is the last car onto the last ferry and that the sedan does not follow him on. However, at the last second, the sedan pulls up, the men inside flash some kind of badges at the staff, and are let on the ferry. The Ghost hops out of his car, and jumps off the ferry, taking his luggage and the manuscript memoirs with him.
Terrified, the Ghost checks into a hotel at the ferry terminal. He calls Robert Rykart, who tells him to stay put. The Ghost is then called by Ruth, who asks hysterically where he is and whether he is alive - they found his abandoned SUV on the ferry. He tells her he is fine, and tells her exactly where he is. While the Ghost waits for Rykart's people to come find him, he searches the internet and googles Paul Emmett. There are a number of articles about the Arcadia Group, and Emmett, and several articles speculate that Emmett has been an agent for the CIA since 1971, a full two years before he would have met Lang at Cambridge. Cruising the Arcadia Group's web page, the Ghost sees that the C.E.O. of Hatherton (a Haliburton-esque organization) is also on the board of the Arcadia Group. He remembers that Adam Lang has a Hatherton jet. He believes he has put it all together: Emmett is a CIA agent who recruited Lang to the CIA in 1973. As Prime Minister, Lang has only made decisions in favour of the US, Hatherton, and the CIA.
Rykart comes to pick up the ghost and they discuss this in a roadside diner. Rykart believes that the Ghost's thesis is correct. He confirms that Lang's stance as Prime Minister was decidedly pro-US and that Rykart was fired as Secretary of State for pointing this out. The Ghost's phone rings, it is Adam. He tells the Ghost he will "swing by" and pick him up on his private jet on his way back to Cape Cod, as Ruth told him where the Ghost was. Rykart tells the Ghost to play along, and so the Ghost agrees to meet Adam's jet at the airport. He is reluctant and is afraid for his life. Rykart tells him that he must get Adam on tape confessing to being a CIA agent.
On the plane, the Ghost tells Adam his theory, that he has been an agent for the CIA since 1973, and Paul Emmett is his handler. Adam is livid and denies it. As they all disembark from the plane in Cape Cod, they are greeted by Ruth, who has come to pick them up, and protesters who are still angry about the torture documents and the ICC investigation. As Adam disembarks from the plane, smiling and waving, the grey haired protester whose son died in Iraq appears on the roof of the terminal, and opens fire. Adam is assassinated.
The Ghost is questioned by police. They take his passport and tell him as a primary witness to the assassination, he will have to abandon his passport. He is stranded in Boston until his agent arrives, some days later, with the Ghost's passport. He is free to go home, to finish Adam's memoirs. The Ghost protests that he cannot write the memoirs now, but we soon see that he has done just that. In his death, Adam has become a hero and his past transgressions forgotten. The memoirs are a bestseller.
Abigail invites the Ghost as her date to the launch party for Adam's memoirs in London, at the Rhinehart Publishing offices. She tells him her marriage did not work out, but she is still clearly grieving for Adam. Ruth gives a touching speech about Adam, as the grieving widow. The Ghost hands Abigail a gift-wrapped package, which is the original manuscript of Adam's memoirs, by Mike McCarra. Abigail also comments that Mike McCarra had said "it was all there in the beginning." This sparks something in the Ghost's memory and he rushes to the copy room with the manuscript. He begins circling the first word of every chapter and it reads: "Ruth was recruited as a CIA agent by Professor Paul Emmett." The Ghost realizes that Ruth's strong influence on her husband ensured he always made decisions in favour of the USA. Lang was never a CIA agent himself, it was Ruth all along.
He rushes downstairs and hands a note to Ruth, who is still speaking, with McCarra's coded message on it. She opens it while still onstage, and it is clear from her face that the Ghost is correct. She makes eye contact with him, panicked. He raises a glass of champagne to her, then becomes lost in the crowd. Ruth is frantically searching for him.
The Ghost races out into the street, clutching the manuscript. He frantically tries to hail a cab and is unsuccessful. He rushes out of the frame, presumably following a cab, and we hear the sounds of a car crash. Passersby stop and stare in the direction of the crash, as pieces of the manuscript flutter across the street.
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