Nina's one task is to keep her family together while a world war threatens to rip them apart.

Warned they "mustn't cry," British teenager Nina Gabriel and her two young siblings board a ship bound for Canada as part of the WWII child evacuee program in 1940. Nina's mischievous brother and seasick sister test her limits on the long voyage-but her burden of responsibility grows still heavier in Canada.

Determined to fulfill her promise to her parents, Nina battles to keep the siblings together through what they all hoped would be no more than one school term. Months turn into years. Unfamiliar Canadian customs, a foster sister who resents them, the mysterious deaths of their host family's other children, and the birth of a new brother back in England complicate Nina's world. It doesn't help when David, the boy she's grown to love, enlists in the air force with no end to the war in sight.

When a telegram arrives after a London bombing, will Nina find a way to fulfill her promise for the brother she's never met? Will the Gabriel siblings learn that each of them is loved, even if they cry?