The more horror I read, the more I’m convinced of an inalienable truth: for a horror story to work, it has to reflect something that terrifies the author. That might be something as simple as an evil clown holding a machete, or it could be something abstract and idiosyncratic. Aoife Josie Clements’s Persona is firmly in the latter category, I suspect, but it isn’t entirely clear just how far its author is willing to go until its conclusion.