An unnamed British ghostwriter (Ewan McGregor) is approached to finalize the memoirs of the former UK Prime Minister Adam Lang (Pierce Brosnan). Strangely, his predecessor, Mike McAra, met his end under mysterious circumstances, with his abandoned vehicle found on a ferry and his body washed ashore, leading to speculation about suicide.
Upon arriving in the quaint yet secretive village of Old Haven, Massachusetts—where Lang resides with his wife, Ruth (Olivia Williams), and an entourage of security—the ghostwriter checks into a modest hotel. Lang's assistant and lover, Amelia Bly (not cast here), imposes strict rules on the writer, particularly forbidding him from taking McAra's unfinished manuscript outside, deeming it too perilous.
As tensions mount, allegations surface against Lang, including serious accusations of illegal actions that could have international repercussions. With reporters and protestors swarming the island, the ghostwriter is moved to McAra’s room at Lang's estate, where he uncovers an envelope holding revealing photos from Lang's university days, hinting that McAra may have uncovered dire secrets about Lang's past. The narrative suggests that Lang has a more complex history than the public knows; he had been part of a political party long before his relationship with Ruth.
During his exploration of the island, the writer meets an elderly local man, who shares a chilling tidbit: the ocean current could not have transported McAra's body as suggested. The old man also mentions strange happenings on the beach the night McAra disappeared, but his claims seem dubious after he subsequently falls and ends up in a coma. Later, Ruth nervously confides in the writer about Lang’s political disinterest and asserts that he often relied on her opinions. After sharing the old man's tale, Ruth rushes out to reflect and later reveals an intense argument between Lang and McAra from the evening before the latter's death. The unfolding drama leads to an unexpected intimacy shared between Ruth and the writer.
Realizing the closeness to his subject may jeopardize objectivity, the writer decides to return to his hotel, opting for McAra's vehicle, which leads him directly to Professor Paul Emmett (not cast here). Emmett, despite appearing evasive, vehemently denies any substantial connection to Lang. The ghostwriter's trip to the professor raises more questions than answers and leads him to suspect a dangerous cover-up.
In a leap of survival instinct, he evades pursuers and returns to the hotel. Still seeking understanding, he once more contacts Rycart for assistance. As they collaborate on the manuscript, hints from McAra’s past materialize, suggesting that the former aide possessed critical information involving Lang’s war crimes with the CIA, widening the conspiracy's implications.
Just as they make progress, the writer confronts Lang aboard a plane, alleging ties to the CIA—a claim Lang mockingly dismisses. However, the shocking twist occurs when a protester assassinates Lang moments after they exit the aircraft, leading to further chaos.
In the aftermath, the writer is compelled to complete Lang's memoir following the assassination frenzy, turning what should be a straightforward biography into a sensational bestseller. Yet, the deeper truth unravels at the book launch, as Amelia inadvertently reveals that the initial chapters of the manuscript concealed secrets threatening national security. It becomes tragically clear that Ruth was recruited by Emmett as a CIA operative, influencing Lang’s political choices.
Heartbroken and betrayed, Ruth receives a note from the writer detailing this revelation. As she processes this devastating news, a sinister turn of fate awaits the writer as he leaves the party—an unseen vehicle barrels toward him, culminating in a shocking hit-and-run that echoes the darkly intricate web of deceit spun throughout the narrative.
