When the Russian Army marches into East Prussia at the end of World War II, the Wolf family flees, but Liesl, Otto, and their baby sister Mia are separated from their mother and they are forced to do dangerous things in order to survive.--

"On a spring morning, neighbors Valentina Kaplan and Oksana Savchenko wake up to an angry red sky. A reactor at the nuclear power plant where their fathers work--Chernobyl--has exploded. Before they know it, the two girls, who've always been enemies, find themselves on a train bound for Leningrad to stay with Valentina's estranged grandmother, Rita Grigorievna. In their new lives in Leningrad, they begin to learn what it means to trust another person....

"After taking down a mole within their organization, the City Spies are ready for their next mission--once again using their unique skills and ability to infiltrate places adults can't. The sinister Umbra has their sights set on recruiting a North Korean nuclear physicist by any means necessary, and the City Spies plan to keep an eye on his son by sending Paris to the chess prodigy's tournaments in Moscow and Beijing. Meanwhile, Sydney's embedded...