Plot?
So this grabber just kidnaps victims, plays a Saw-like game with them, toys with them before killing them. Room is sound proof and in the basement where he one day intentionally leaves the door open for the kid/s to try to escape. Once they try to escape, he is there waiting for them upstairs with a daddy beats yo'ass to death belt. Only reason it doesn't happen in this movie is because of the so-called black phone that for some reason holds the souls of the previous dead victims that warns/spirit guides the protagonist not to fall for the trap door and the things they've done to try to escape. They devise a plan to eventually kill the grabber. The end. That's it? Both kids have some special spiritual power from their mom.
I hear it relies heavily on jump scares to give some aspect of horror to the show.