Lo Blacklock, a journalist who writes for a travel magazine, has just been given the assignment of a lifetime: a week on a luxury cruise with only a handful of cabins. At first, Lo’s stay is nothing but pleasant. But as the week wears on, frigid winds whip the deck, gray skies fall, and Lo witnesses what she can only describe as a dark and terrifying nightmare: a woman being thrown overboard. The problem? All passengers remain accounted for --- and so the ship sails on as if nothing has happened, despite Lo’s desperate attempts to convey that something (or someone) has gone terribly, terribly wrong.