With their second child due to arrive any day, it would be reasonable for Jonathan and Frances Healy to stay safe at home. Unfortunately, the world has other ideas. A postcard from the mysterious coastal town of Gentling, Maine has Jonathan packing his bags and preparing for an adventure—and when did Fran ever pass up an adventure? But the people of Gentling aren't just ordinary fishermen and sailors: they're the descendants of finfolk who fell in love with the humans who pulled them from the sea, and they have long since settled into a gentle rhythm of a life lived between the wet and the dry. Only now, someone or something is stealing their babies from the shore, endangering the next generation. Old obligations and new obligations will collide, and the newest member of the Healy family will join the fight...or will she? Because it's not just the babies of the finfolk who are in danger, and unless they're careful, Johnny and Fran might find themselves losing another child...