The Letter follows the life of Tina in the 1970s who seeks respite from her abusive marriage by volunteering at a charity shop. One day, while sorting through the pockets of a second-hand suit, she comes across an old letter. It is still firmly sealed and un-franked. Unable to resist the pull of curiosity, Tina opens the letter. It was written on 4th September 1939. She is so moved by the contents and bemused as to why the letter was never delivered, she embarks on a quest to find out what became of the writer and his intended recipient.

The mystery of how this love letter ended up in Tina’s hands is also uncovered through Billy’s story from the early 1940s. He writes a letter that will change his life forever, unaware that it will not be read for another 34 years, and then by a complete stranger.