When a fall from the mast leaves Alba unable to sail, he finally has the chance to run away from his family debts in search of a better life. He hopes to reunite with his mother, Edythe, where they always promised to meet, but finding the town of Moon Harbor proves a greater challenge than Alba expected. Worse, upon arriving, no one seems to know anyone by the name Edythe.

Taking a job as the local lighthouse keeper while waiting for her to come, Alba attempts to find peace in his stolen freedom—but the sea has other plans. First come the shadows, then the voices, then watery trails left on the floor. He's inundated with erotic dreams of sirens calling to him, and distant singing haunts his waking hours.

After a debtor catches up with him and he's forced to dispose of their body, Alba is interrupted by Eridanys, the last merrow of Moon Harbor, who curses him from leaving until he can find out what happened to the other merrow that once filled those waters. Eridanys' demands are exhausting and endless—but as their relationship deepens, and Moon Harbor's secrets are butterflied open to see, it becomes clear they may both be prey to the town.

Contains mature themes.