One day he falls victim to the sinister masked figure (Ethan Hawke) and finds himself locked in a stark soundproofed basement.
On the wall is a disconnected phone but it starts to ring and the voices on the other end begin to offer him advice on how to escape.
Meanwhile his sister Ginny (Madeleine McGraw) is having visions of the Grabber that might lead her to him.
This Blumhouse offering mixes supernatural elements into a fairly standard serial killer horror. It's very very mild, with almost no violence or nastiness but it is very stylishly done.
The child actors are excellent, Ethan Hawke is quite creepy but not on screen much.
What it does really well is imbue all the minor characters (mostly previous victims) with life through visions/flashback so you care about them. Ginny has a fair bit to do and is well written compared to the absolute one dimensional cypher you'd expect from "protagonist's kid sister" and the town feels like a place rather than a location.
Nothing unexpected or thrilling happens at all but it's so well constructed and paced I highly enjoyed it 7/10. Once it appears more widely on streaming check it out if you like the occasional mild bit of horror. It's _very_ mild but this does it no harm and maybe makes it work for a different audience.