In the year 2019, an unknown plague has transformed the world's population into vampires. As the human population nears extinction, so does the blood supply. Now the vampires must find a blood substitute before time runs out. Researcher Edward Dalton and a clandestine group of vampires have made a remarkable discovery, one which has the power to save the human race.

Two strangers meet by chance, spend a night together in Vienna, and part before sunrise. Nine years later, Jesse has written a book about the encounter. During his accelerated European book tour, he meets up with Celine in Paris. Before Jesse's flight home, he joins Celine for a picturesque walk around the city and they have an intimate conversation, ending at Celine's apartment. Will they get the chance to fall in love all over again?

Jesse and Celine first met in their twenties, as seen in Before Sunrise, reunited in their thirties in Before Sunset and, now they face the past, present and future, family, romance and love. Now on a writer's retreat in Greece, the couple looks for a night of passion, but instead their idyllic night turns into a test of their relationship and a discussion of what the future holds for them.