I'm trying to remember a movie in which aliens or some kind of monsters were able to cause power outages. When in darkness, they'd drag their victims to the darkest corner and transfer them into some sort of a dark dimension, not unlike Upside Down in Stranger Things.
There was a group of people who figured it out. They get kidnapped one by one, including one that gets dragged under an elevator.
It's happening everywhere.
The movie ends with the main character (a woman) in an asylum for insane people... dragged into a closet. She's then shown in the dark dimension, banging on an invisible barrier, yelling for help. Some people walk into a room, don't see anyone, close the closet. When it's closed, the alien/monster bites her face. Screen goes dark.