Had a dream last night (or this morning, more properly) in which a group of kids went exploring through a door (which had appeared in a hillside where they liked to play) to a house on the other side. The door closed, and at least some of them were trapped on the wrong side. Probably kids from both worlds, because a long section of the dream involved a kid trapped in a ghostly existence on one side trying to convince the mother of a missing girl (trapped on the other side) that her daughter wasn't dead. The kids could apparently all see each other, though - why? Maybe because they met at the doorway? Maybe because they'd all gone through it at least once?
There was also a lot of waiting to see if the door would open again, and - when it did - trying to see if they could get through quickly enough to get everyone back to the correct world (where people could see them) before the door closed again. They couldn't just camp out in front of the door, because even though they were invisible they still needed to eat, and do all the little things that people have to do.
There was also, semi-randomly, an avalanche; but if I were telling this as a horror story I think I'd just leave that part out.