The final novel in the Mermaids and Merliens series.

Mercadia is void. Earth is next. Long live Mercadia.

Magic and madness arrive in full force at the Jersey Shore. Humans are transforming, the government is capturing and experimenting on anything with a tail, and Jonah and Mezzy are caught in a complicated net of flourishing romance and floundering loyalties.

Having narrowly survived their home world's apocalypse, displaced mermaids are no longer wandering spectators in their own story. Out of the ocean, they march up the coast, casting deadly sorcery and leaving chaos in their wake. In the end, there may not be any land or sea remaining for anyone.

The line between human and merlien is thinning. Choose a side and swim on. For Earth or for Mercadia.

Forever.