Emma and Lucy are starting Year Nine, still reeling from the adventures that they had the summer before. They would do anything to see Meg again, especially since they read the letter that she left them. But when their wish comes true, nothing could have prepared them for the revelations they have to face. They are joined by Rich, originally from Poland, and Ada, a Jewish woman who has seen first-hand, the horrors that the Nazis can inflict. They must work together to crack the codes and rescue as many of Ada's hidden friends as they can. Will they be able to find them? What risks are they prepared to take? And why does it seem that the library holds the key to allow them to cross back and forth through time? Once again, Emma's friendships are put to the test as VE Day still seems a long way off.