This formulaic horror movie serves mainly to illustrate what a resourceful actor Ethan Hawke has become; as a washed-up true-crime author desperate for a hit, he plays on his boyish energy to suggest a darting intelligence beneath the character’s vanity and opportunism. The writer discovers a supernatural entity while investigating a series of unsolved murders, and in a twist that’s likely to please celluloid buffs, the creepiest evidence comes from eight-millimeter film reels he must splice together himself. Most of this takes place inside the character’s house, and writer-director Scott Derrickson (The Exorcism of Emily Rose) turns in some resourceful work too, finding new ways to frame the same rooms from one scene to the next and providing comic relief whenever the action threatens to turn monotonously grim.