Nine wonderful years have been passed, since the movie Before Sunset. Jesse and Celine married each other, having twin girls. Jesse has to struggle to continue his father-son relationship with his son, Hank who is with his mother in Chicago. His ex-wife is a novel writer with her high success in the career. Celine is looking for a job with French govt.
Hank spends a good time in summers with Celine and Jesse on Greek peninsula. But he feels that he couldn't become a good father when he is at the airport to drop him for his flight home. Then Celine and Jesse have some discussion on Hank, then on her career. They talk more of love and life while having dinner. For letting them a night alone, their friends had booked a room for them. While on their way, they remember the night at Vienna.
They prepare for making out and get intimate, but are interrupted by Hank's phone, who has developed more of a good bonding with Celine than Jesse. They get into a worsened argument, with some fear of their present and future. Jesse insists to move Chicago, so that he could remain close to Hank, while Celine wonders what about her career. And she says that she no longer loves Jesse.
Celine leaves the room and goes in the restro. Jesse comes at the place. He tells that he is a time traveler, with a reference to the first night defining to be the best of their life. Celine tells that the fantasies don't come out to be true. After a while, Celine joins him in his fun and they both are together again.