In 1921, residents of the village of Charlton Ambrose planted eight ash trees in memory of those who fell in the First World War, but at night someone secretly planted a ninth tree - in memory of the “unknown soldier”. Eighty years later, journalist Rachel Elliott, wanting to save the memorial ash grove from being cut down by a developer, tries to solve the mystery of the ninth tree. The girl's search leads her to her own family secrets and the story of a great and tragic love that once unfolded against the backdrop of the battles of the First World War.