The Return by Rachel Harrison

"An edgy and haunting debut novel about a group of friends who reunite after one of them has returned from a mysterious two-year disappearance. Julie is  missing, and the missing don't often return. But Elise knows Julie better than anyone, and she feels in her bones that her best friend is out there, and that one day she'll come back. She's right. Two years to the day that Julie went missing, she reappears with no memory of where she's been or what happened to her. Along with Molly and Mae, their two close friends from college, the women decide to reunite at the eccentric, remote Red Honey Inn. But the second Elise sees Julie, she knows something is wrong--she's emaciated, with sallow skin, chipped teeth and odd appetites. In so many ways, Julie seems to be the friend they all loved and lost. But in others, she seems to be a stranger. When bad weather traps them inside the hotel, tensions flare. Elise begins to hear scratching within the walls, to see the slither of shadows cast by nothing. And as the weekend unfurls, it becomes impossible to deny that the Julie who vanished two years ago is not the same Julie who came back. But then who--or what--is she?"