In 1913 Rosa, an English girl and the American Lily meet each other at an international school in Switzerland and form a firm friendship. Over the next few years, against the backdrop of the First world War, both together and individually, they face a range of experiences and emotions including love, death, tragedy, despair and resilience. However, just beneath the surface lurks a scandalous secret of which neither Rosa nor Lily is aware, but which nevertheless has the power either to bind them closer together or indeed to tear them apart forever...