It has been nine years since we last met Jesse and Celine, the French-American couple who once met on a train in Vienna. They now live in Paris with twin daughters but have spent a summer in Greece at the invitation of an author colleague of Jesse's. When the vacation is over and Jesse must send his teenage son off to the States, he begins to question his life decisions, and his relationship with Celine is at risk.

Nine years later, Jesse travels across Europe giving readings from a book he wrote about the night he spent in Vienna with Celine. After his reading in Paris, Celine finds him, and they spend part of the day together before Jesse has to again leave for a flight. They are both in relationships now, and Jesse has a son, but as their strong feelings for each other start to return, both confess a longing for more.

Isabelle, a geneticist recovering from a toxic marriage, is raising her only daughter, Zoe, with her contentious ex-husband. Zoe means everything to her mother and so when tragedy strikes the fractured family, Isabelle travels to Russia in seeking the help of a world-renowned fertility physician who Isabelle believes can help bring back her little girl.