Some of the intruders in Juan Carlos Fresnadillo's dense, dark, but not very scary thriller come not from outside but from within. Or maybe both. Like the specter that creeps into the Madrid apartment where Juan lives and attacks his mother. Is he real or a dream? Same goes for the entity that 12-year-old Mia (Ella Purnell) thinks is lurking in her closet in London. And what connection does this spook have with the hand-written ghost story Mia finds in a box in a hole in a tree? Fresnadillo dexterously interweaves these tales, maintaining the mystery, making you wonder whether it's time to call in Mia's dad (Clive Owen), or Fr. Antonio (Daniel Brühl), or Dr. Rachel (Kerry Fox), or maybe the team from Ghost Hunters. But when the most pulse-pounding moments involve a burning overcoat or a glimpse of an arm in a surveillance video, the threat of inner and outer violation remains more theoretical than palpable.