Based on the short film by Andres Muschietti, 'Mamá'. Here's a clip (or maybe it's the entire short, I'm not sure). Very impressive directing/camera. Check the hand placement on the rail at 1:06 and how the camera frames it -- not an accident. The steady shot down the stairs is good work. Muschietti did a great job working with kids, getting compelling performances from them. The girl's entrance is one of the creepiest visuals I've seen.
Very well done. I don't even care about most efforts. They're not scary, have no spine, are not engaging. This, however, hits the mark. Good, good stuff. Wow. Yes. Waiting. 'Mama' will be one to see and Muschietti is one to watch for.