A new island has popped up between Ankh-Morpork and Al-Khali, setting the stage for a political crisis that could bring about war for the first time in more than a century. Rather than share the island, each nation lays claim to the whole enchilada. But there is hope. Leonard of Qurim can invent a "Going-Under-The-Water-Safely Device", if not a name for it, and equip it with weapons so frightening no one will want to fight. It's brinksmanship Discworld-style in this new addition to the series that hilariously goes where no fantasy has gone before.