Clayton Hammond (Dennis Quaid), a famous author, attends a public reading of his new book, The Words, centered on Rory Jansen (Bradley Cooper), an aspiring writer who lives in New York City with his girlfriend, Dora (Zoe Saldana). With the help of his father (J. K. Simmons), Rory gets a job as a mail supervisor in a literary agency and attempts to sell his first novel, which is repeatedly rejected by publishers.
After living together for some time, Rory and Dora marry and, during their honeymoon in Paris, Dora presents Rory with a gift, an old briefcase from an antiques store. Returning to America, Rory finds an old but masterfully written manuscript in the briefcase with a central character named Jack. Rory types the manuscript into his laptop. Later, while using the laptop, Dora happens upon the novel and reads it. Assuming her husband wrote it, Dora encourages him to meet with a publisher, Joseph Cutler (eljko Ivanek), who offers Rory a contract after reading the manuscript, which Rory accepts. The book is a hit and Rory becomes famous.
At this point, Hammond takes a break from the reading and goes backstage, where he is introduced by his agent (John Hannah) to Daniella (Olivia Wilde), a student and amateur writer who wants to interview him and notes that he is separated from his wife, although he still wears a wedding ring. Hammond agrees to meet her after the ceremony and returns to the stage, where he continues to read the book.
The second part of the reading details Rorys encounter with an unnamed old man (Jeremy Irons) in New York City's Central Park, who reveals himself as the true author of the manuscript and that it was based on his life in Paris. Irons's character explains that he was a young man (played by Ben Barnes) when first stationed in France by the US Army in the final days of World War II where he fell in love with Celia (Nora Arnezeder), a French waitress. They eventually married and had a daughter, but the baby died shortly after birth. Unable to cope with the loss, Celia left him and moved to her parents' house. He then used his pain as inspiration to write the manuscript, which he took to Celia while visiting her at her parents home. She found the story so moving that she chose to return to him. However, she unintentionally left the manuscript in a briefcase on the train after her trip back to Paris, thereby losing it. The scene shifts to the present and the old man explains that he and Celia tried to repair their marriage but they eventually divorced. Irons's character leaves Rory sitting alone on a park bench.
The public reading ends and Hammond tells his fans they must buy the book to learn how it ends. Daniella then accompanies Hammond back to his apartment where she pressures him into telling her more. Hammond explains that Rory tells the truth about the creation of the story, first to his wife and then to Cutler, his publisher. Also, Rory tells Cutler he wants to credit the old man as the true author. Cutler angrily advises against this as it would severely damage both their reputations and recommends giving the old man a share of the book's profits instead.
Rory then seeks out the old man to pay him and finds him working in a plant nursery. Irons's character refuses the money but, after doing so, reveals that while once riding a train to work, years after his divorce, he spotted Celia with a new husband and a baby girl at a train station. The old man points out that people always move on from their mistakes as Rory will too.
Daniella continues to pressure Hammond for more details. He reveals that the old man dies not long after Rorys second meeting with him along with the secret about who the manuscript's author really is. However, Rory cant move on emotionally and is tormented by nightmares until he focuses his grief on another book, one that allows him to tell the true story of the manuscript.
Impressed with this, Daniella passionately kisses Hammond on the mouth but he pulls away, apparently unsure about whether to become romantically involved with another woman. However, in that moment, he remembers Rory lying in Dora's arms as she tells him everything will be alright, suggesting The Words is an autobiographic book with Rory as Hammond's surrogate.