England, 1943: Home is no longer safe for eight-year-old twins Molly and Jacob. Night after night wailing bombs and screeching planes skim the rooftops overhead. They cradle each other, shivering in terror, not knowing if they will live to see dawn. Their mother, Martha, has no choice but to evacuate them to the safety of the countryside.

At the train station, Martha bites back tears as she says goodbye to her precious children. Knowing she might never see them again, she gives Jacob a letter, pressing the envelope into his hands and telling him to only read it if they are in danger.

In the country, Molly and Jacob must adjust to life with strangers. Every night they dream of returning home to the arms of their beloved mother. But then the unimaginable happens. Martha is killed in an explosion, leaving the twins all alone in the world.

The war has robbed Molly and Jacob of everything – all they have left is one another. Motherless and destitute, they face the grim reality of life in an orphanage. The time has finally come for Jacob to open the letter. What secret does it hold, and could it change the course of their tragic fate? Because if they are together, they can survive anything – but what if they are torn apart?