It's November on the coast of Maine, and Luna is spending a week at her uncle's fishing camp near the village of Frenchman's Cove. The camp sits at the end of a long gravel road, and at the end of that road is a pier that juts into the fog. On the second night, she hears a sound she can't place: a low, rhythmic drumming, muffled and wet, as if something is being struck far beneath the water. The local lobsterman, Elias Vane, tells her it's nothing—just the tide working on a loose plank. But the sound has a pattern, a kind of counting, and it seems to move along the coastline as if following something. Luna rows out to the pier's end alone, and what she finds there isn't a loose plank. It's a message, written in a language she almost understands, and a hand that reaches up from the dark to correct her reading.