During a stay in Paris in 1957, an American girl Clara Foy learns that her mother Lauren had an illegitimate child when she was a teenager living in California. The little girl was immediately given up for adoption. For Lauren and her family, this was a scandalous event that has been kept a guarded secret until the present moment, when the lost little girl comes onto the scene, now a young Parisian woman named Emma Dusel. Her identity fills Clara with complicated expectations, especially when she learns that Emma's resentment of Lauren and the abandonment she represents has almost destroyed Emma's life. With the aid of Emma's birth father, an Irish painter now living in Paris named Jack Roman (with whom Lauren has fallen in love once more despite the deep threat that that brings to her own marriage and family), Clara attempts to bring about a reconciliation between her new sister and her mother. The effort puts Clara's own relationship with her mother in jeopardy, the woman Clara loves more than anyone else.