The Caerleon Imperium is in decline. Five thousands years of prosperity have been followed by a long era of institutional and moral decay.

Lady Elaine Greymoor awakens imprisoned aboard a ship bound for deep space. When she is rescued by the King of Pirates, Ulysses, Elaine soon realizes she has merely exchanged one cage for another. Forced to serve aboard a vessel with fellow prisoners of war, Elaine and the rest of the Sunless Fleet race against the imperium, who will stop at nothing to retrieve the legendary Chalice of Time, the empire's last chance to return to its ancient glory.