Mosca Mye has spent her life in a miserable hamlet, where her father was banished for writing inflammatory books about tolerance and freedom. Now he is dead, and Mosca is on the run, in search of a better life. With Eponymous Clent, a smooth-tongued swindler, she heads for the city of Mandelion, living by her wits among highwaymen and smugglers, dangerously insane rulers, secret agents, and radical plotters.

But the city is in uproar, for someone is once again printing seditious material, and no one is quite what they seem. With suspicion and peril at every turn, Mosca uncovers a shocking plot to force a rule of terror on the people of the Realm, and all too soon merry mayhem leads to murder.

Funny, surprising and fantastical, with an unforgettable cast of characters, Fly By Night contains at its heart an inspiring truth: that the power of books can change the world.