Urban legend has it that if you knock (twice!) on the door of an abandoned old house, a demonic witch is awakened. Believing this to be true, troubled teenager Chloe (Lucy Boynton) goes ahead and bangs away, thus dooming herself to an ordeal in which -- after moving back in with her junkie-turned-sculptor mom (Katee Sackhoff) -- she’s pursued by the evil hag. Prefacing her every arrival by turning off the lights and resembling a more aged and gaunt variation of The Ring’s stringy-haired ghoul Samara, this malevolent being behaves a lot like her horror-cinema predecessors -- which is to say, she taunts more than she actually terrorizes, preferring to jolt her would-be victims rather than just, you know, kill them. Thanks largely to images of an old-lady specter materializing in the dead of night, director Caradog W. James shows enough visual flair to suggest that, with better material, he might be able to generate some memorable frights. As it stands, however, Mark Huckerby and Nick Ostler’s screenplay is a rickety affair that attempts to generate mystery about which person is responsible for first creating this supernatural situation, even though the film contains only four characters -- and two of them are clearly not the culprit. Consequently, Don’t Knock Twice proves merely a collection of decent scary sights tattooed onto a senseless story.