In 1941, amidst the turmoil of German occupation on the island of Guernsey, a group of four friends finds themselves perilously halted by soldiers while violating curfew. To evade arrest, they concoct a swift excuse, claiming they were returning from a book club meeting, whimsically dubbed the “Guernsey Literary and Potato Peel Pie Society.”
Fast forward to January 1946, where author Juliet Ashton, portrayed by Lily James, is busy promoting her latest literary work penned under the pseudonym Izzy Bickerstaff. With the help of her publisher, Matthew Goode as Sidney Stark, she embarks on writing insightful articles for The Times Literary Supplement, focusing on the profound impact of literature.
Juliet receives a heartfelt letter from Dawsey Adams, played by Michiel Huisman, a resident of Guernsey who has acquired her edition of Charles Lamb's Essays of Elia. In his note, he inquires about a bookshop in England to find another work by the same author and mentions his involvement in the book club that gathers weekly. Eager to learn more about this intriguing society, Juliet sends an exchange of Lamb’s writings and asks for details of their gatherings.
Keen to explore this unique community, Juliet plans a visit to Guernsey, ignoring Sidney's concerns. Before departing, her American boyfriend Mark Reynolds, portrayed by Glen Powell, proposes to her, and she accepts.
Upon her arrival, Juliet is welcomed as a special guest at a society meeting. The members — including Dawsey, Amelia Maugery (played by Penelope Wilton), Isola Pribby (portrayed by Katherine Parkinson), Eben Ramsey (played by Tom Courtenay), and young Eli Ramsey, become enamored with her presence. However, they reveal that Elizabeth, the society's founding member, is currently away. Dawsey is looking after her daughter, Kit (played by Kit Connor), who affectionately calls him "dad." Juliet requests to write an article about the society, but Amelia expresses concerns about this idea.
Instead of returning home, Juliet decides to extend her stay under the pretense of researching for a new article on the German occupation. She uncovers hidden truths about Elizabeth, who was arrested and sent to Germany during the war, while her friends maintain hope for her return.
Juliet seeks assistance from Mark, who is actively serving in the armed forces, asking him to help track down Elizabeth. Conversations with her landlady reveal unsavory rumors about Elizabeth, indicating her complicated past with the occupying German forces.
In a heartfelt exchange, Dawsey discloses that he is not Kit's biological father; instead, Kit's real father was a German doctor named Christian Hellmann who had served alongside Elizabeth at the local hospital — a man whose life ended tragically when his ship sank on its way back to Germany.
Mark's arrival in Guernsey leads to tensions when he questions Juliet about her missing engagement ring. He brings grim news regarding Elizabeth, informing the society that she was taken to the Ravensbrück concentration camp and ultimately killed while trying to save another prisoner.
After returning to London, Juliet struggles to readjust to her former life, leading to the dissolution of her relationship with Mark. She channels her experiences into writing about the society and, once her manuscript is completed, shares it with Sidney and sends a copy to the society in Guernsey.
In a moment of vulnerability, Dawsey reads Juliet's heartfelt letter to the group, realizing that she has ended her engagement. He sets off to find her in London, just as Juliet plans to return to Guernsey. Their paths cross as she boards the ferry, leading to a touching reunion where they both propose to each other simultaneously.
As time passes, Dawsey reads to Kit from Tales from Shakespeare, with Juliet by his side, both wearing wedding rings. The film concludes with the Society's next meeting occurring off-screen, featuring Sidney as they joyfully share literary excerpts and engage in thoughtful discussions.
