The doors are showing up as people are killed this week.

[ That at least clicks, and Break frowns. He's thoughtful for a moment, but he nods slowly, though Undyne may not actually like what Break has to say. After all, it does imply that he knew that more people would be dying this week. ]

...It could be because they're sacrifices to the demons. They're different, somehow, but I didn't find out what the specific reason was. Just that it was necessary.