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 as a junior reporter for a teen lifestyle site as she follows the daughter of a British billionaire on tour with the biggest act on her father's music label to uncover what links both the band and the billionaire have to a recent threat from an old Soviet missile base. From a daring break-in at one of London's most exclusive homes to a dangerous undercover mission to a desperate search and rescue operation on the streets of Beijing, the City Spies have their work cut out for them on their most dangerous mission yet.