Meg Kenyon's father is fighting with the Allies in France, but she is beginning to lose hope of ever seeing him again as the war rages on. To make matters worse, she learns that her father is now a prisoner of the Nazis. The only connection Meg has left of her father are the codes he placed in a jar for her to decipher and even those are running low. But when Meg finds an injured British spy in her grandmother's barn, she embarks on the adventure of a lifetime to help a family of German refugees across Nazi-occupied France to neutral Spain along with a final code from Papa to help complete the mission. As Meg is able to figure out more of her father's clues, the more dangerous her journey becomes.