There is so much evil in the world ... but this one thing we can make right.

The island colony of Arcadia promises hope, prosperity, and tolerance to all who settle there ... and asks only that they protect it with their lives. For Caroline and Jo, however, this opportunity could spell disaster, for the island's owner is none other than Mrs. Masterson. Is her invitation an honest offer, or a deadly lure? And what relation does this Arcadia have to the one in the widow's paintings—a place accessible only by magic, and the last known location of the monster called Leviathan?

To uncover the truth, Caroline and Jo set out for Arcadia, only to find that each of their fellow travelers has personal reasons for accepting Mrs. Masterson's offer. Caught between this impromptu army and the might of England and France, knowing at any moment the Leviathan might reappear, they race to stave off the impending violence.

But the further they get, the more they realize that Mrs. Masterson has set herself, and the Leviathan, against a far greater opponent than any one nation. Her success will mean catastrophe for millions, but stopping her may cost Caroline and Jo what they hold most dear: each other.