From the first time she heard the unforgettable melody her father whistled, Mabel Shields was determined to unlock the lyrics to this haunting tune, a relic of his time in the Great War. A curiosity that led her to meet Paul Conway, manager of Barwell's struggling music shop. Mabel begins to share Paul's interest in cinema as well as appreciate his extensive knowledge of popular music. Odeon matinees together and lyrics as coded love letters chart their growing closeness as the cost of the war bears down more heavily on their lives, living in fear, under ever tighter restrictions, and losing loved ones.

And what happened to her, while rushing home through a blustery storm one Christmas eve years later, that brought it all back?