Twelve years ago, on a moonlit rooftop above Washington Square, Lyla Novacek (Keri Russell), a sheltered young cellist, and Louis Connelly (Jonathan Rhys Meyers), a charismatic Irish singer-songwriter, were drawn together by a street musician's rendition of ''Moondance'' and fell in love. After the most romantic night of her life, Lyla promised to meet Louis again but, despite her protests, her father rushed her to her next concert--leaving Louis to believe that she didn't care. Disheartened, he found it impossible to continue playing and eventually abandoned his music while Lyla, her own hopes for love lost, was led to believe months later that she had also lost their unborn child in a car accident. Their orphaned son (Freddie Highmore) uses his musical talent as a clue to find his birth parents.