As the town that produces probably the most selium – that precious gas that elevates airships and capabilities strange magic – Hond Steading is a jewel value stealing. To shoreline up the city’s defenses, Detan claims his aunt that he’ll recover Nouli, the infamous engineer who built the hundred years gates that defend the imperial capital of Valathea. But Nouli can be imprisoned in the Remnant Isles, an impervious island jail run by the empire, and it’s really Detan’s mistake. Detan doesn’t dare approach Nouli himself, therefore his companions volunteer to obtain themselves locked up to get hold of Nouli and convince him to help. Now Detan has to break them all out of jail, and he’s going to need the help of a half-mad doppel to accomplish it.