A once-in-a-lifetime opportunity presents itself for a talented British screenwriter known simply as "The Ghost" (Ewan McGregor) as he agrees to complete the memoirs of the British prime minister Adam Lang (Pierce Brosnan). The Ghost soon learns that he has replaced the prime minister’s former aid after he died a mysterious death.

As soon as The Ghost touches down in the remote mansion in the US where Lang is staying, Lang is accused of committing war crimes. The Ghost continues his research into Lang and into the unfinished work of his former aid, he soon finds that his aid died because of what he knew; that Lang was involved in a conspiracy with the CIA. The deeper The Ghost delves, the more his life is put in danger!