Travel magazine writer Lo Blacklock has just been given the assignment of a lifetime: one week on a luxury cruise with only a handful of cabins. The sky is clear, the waters calm, and the elite guests jovial as the exclusive cruise ship, the Aurora, begins her voyage in the picturesque North Sea.

At first, Lo’s voyage is perfect, with a plush cabin, elegant dinner parties, and plenty of relaxation. 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 has gone terribly, terribly wrong…