"Benigno "Benny" Caldera knows an orphaned Boricua blacksmith in 1910s New York City can't call himself an artist. But the ironwork tank he creates for famed Coney Island playground, Luna Park, astounds everyone, especially the eccentric side-show proprietor who commissioned it.

Benny's work earns him an invitation to join the show's eclectic crew of performers--his first welcome in the city--and share in their astonishing secret: the tank Benny built is a cage for their newest exhibit, a living, breathing, in-the-flesh merman stolen from the banks of the East River under a gleaming full moon. Despite their different worlds, what begins as a friendship of necessity deepens to love, leading Benny's heart into uncharted waters where he can no longer ignore the agonizing truth of Río's captivity--and his own. A cage is no place for a merman to survive.

Though releasing Río means betraying his new family, bankrupting their home, and losing his soulmate forever, Benny must look within for the courage to do what's right, and find a love strong enough to free them both.