Something unspeakable has happened to sisters July and September. Desperate for a fresh start, their mother Sheela moves them across the country to an old family house that has a troubled life of its own. Noises come from behind the walls. Lights flicker of their own accord. Sleep feels impossible, dreams are endless. In their new, unsettling surroundings, July finds that the fierce bond she's always had with September -- forged with a blood promise when they were children -- is beginning to change in ways she cannot understand.