Like genre masters before him, director Mike Flanagan’s personal addictions inform his storytelling, to a terrifying effect — Anyone who’s been hooked on opioids and weathered withdrawal can tell you it’s the stuff of nightmares. Hell. I’m haunted by my own addiction, which, the therapist and anonymous oldtimers say, is lurking around a dark corner, getting stronger, “doing push-ups,” waiting to meet me unawares.