Sara Martinez is a hacker facing years in juvenile detention, until she meets Mother, a spy who gets her out of jail and into MI6, British Secret Intelligence. Operating out of a castle in Scotland, the City Spies are five kids from around the world who've fallen through the cracks only to form a family like no other. When they’re not at the local boarding school, they’re mastering spy skills like sleight of hand, breaking and entering, covert observation, and explosives. So they can go places in the world of espionage where adults can’t.