Women are being murdered. Sirens are blamed. Age-old prejudice may turn deadly...and the assassi is loving it.

Piper, Dax, Dylan, and Max have settled into a rhythm: scout the alt-worlds, investigate the target, hunt the assassi, bring them home for execution, rest, and repeat.

But calm seas never last.

When an assassi murders two of their own, Piper is truly afraid for the first time in years. This unknown assassi wields a horrifying curse forged by Poseidon to use against women?especially winged women?and hides among pirate-infested islands where sea monsters lurk on the horizon and misogyny runs deeper than the reefs.

Despite these fears, Piper and Dylan are determined to find their friends' killer before more bodies are cast upon the shores. And if a captured goddess is right, they can save the winged women of this alt-world in more ways than one...

In the skies of this Caribbean world, Poseidon-cursed sirens fly on Persephone-blessed wings and yearn for a life where men no longer control their fate. If their song fails to lure a mate, they sink beneath the waves to become bloodthirsty mermaids. The few who escape their curse and become siren wives are often distrusted as lying temptresses, despite the good luck their wings bestow.

As murders rise, old prejudices become new persecution. Poseidon's faithful turn on the sirens, blaming them for the deaths?and perhaps taking their cue from Poseidon himself.

Only Barth, a man forever cursed with bad luck, can prove the sirens' innocence. Working secretly against a conniving merchant and a self-righteous widow hell-bent on destroying the sirens, Barth guides Piper and her Sanctuary team's hunt for the real enemy: the elusive, women-killing assassi prowling the islands' shallows.

But luck is not on their side. And even the lucky can fall before the curse of a god.